To speak of "the religion" of the ancient Egypt can seem a nonsense. On close to 4000 years of evolution, the religious ideas indeed varied considerably, and it would be more discriminating to speak of "the religions" of Egypt.
Nevertheless, there exists diverse threads, of great basic ideas which remained sufficiently steady thanks to the fundamental conservatism of Egyptian civilisation to permit to propose a reasoned approach. Gods and goddesses are everywhere, from minor household figures - such as Bes or Taweret - to the all-powerful gods of empire, Amun and Re. This made Egypt the most completely theocratic society of the Ancient world and its inhabitants "more religious than any other people" (Herodotus).

The Egyptian man is entirely dependent for his survival on the specific geoclimatic nature and conditions in the valley of the Nile. The impossibility of him understanding the reasons for the phenomena and natural events comes with an inability to act on them.

Not being able to understand them, he describes them in the form of divine entities, which will associate with each a person and a function.
The typical example is the one of the sky: it can be represented like an arch, a reminder of its physical reality, but also as a woman (Nut) or like a cow (Hathor) since the function of the sky is to return the sun to the world every morning.

But this is not all. It is also necessary that the divinity is included in the Egyptian order, in a recognised social group, the one of the gods.
For this, it is going to be necessary to represent the god like a human being, anthropomorphosis, to make it become a "divine person".
It is also necessary to give him a name, which is make it possible to come into contact with him.
The god's representation often combines a human body (his/her persona) and a head constituted by animal or even by an object, vector of the function which one wishes to see exercised at a specific time and situation.
It is not necessary to believe that an animal representation has an unambiguous significance. It often covers all a world of meaning.
Thus, the ram will be taken as an image of virile fertility in some circumstances, and as a representation of the Ba of Re elsewhere. The world of snakes also covers entities in extremely diverse meanings.

A representation of an Egyptian god has therefore to be understood as an icon, but which we cannot entirely trust to know with whom we are dealing.
In fact, the functions are interchangeable, a divinity is capable of borrow a function of another or combining the different functions which were not attributed to him originally.
So, while looking at an image of an Egyptian god, it is always necessary to look for the additional elements, and in particular its name, to identify it.

The gods are responsible, by their functions, for intervening by beneficial manifestations or even for nature. Man is therefore under their total dependence and must absolutely be able to influence their behaviour to render them favourable.
According to the traditional way of thinking of the reciprocity ("a favour for a favour"), the human and divine worlds are interdependent. Men need the gods, but the gods all have as much need for men. It is the basis of a religious system.
Indeed, if they are no longer worshipped, if the offerings are no longer presented to them the gods decline and die. Because the Egyptian gods are mortal!
And it is necessary to note that this original concept at the very least was was seen to be just : when, toward the 5th century of our era, the temples finished and all ended up closing under the pressure of the triumphant Christianity, the former gods who had governed the two lands for nearly 4000 years will be forgotten, forsaken and will in fact disappear…

So divine worship is an obligation. It will address either the person or the god's function.

Worship of the divine person is specific, and represents the secluded worship of the divinity. By definition it doesn't apply to another divinity.
To compensate this particularity, which the Egyptian order hardly appreciates, appears at the same time as a worship of the function, which will be more or less standardised country-wide since the functions can be interchangeable: it is the daily divine worship.

Worship takes place in the temple, traditionally described by Egyptologists as a magical microcosm, by a group of specialised civil servants: the priests. Sauneron and Yoyotte proposed the analogy with a "nuclear power station": an isolated, protected place ("Djeser") where are confined the gigantic divine forces which are set in motion; a place which must remain absolutely separated from the common world because any incursion here in these processes would be likely to induce a cosmic catastrophe.

The role of the priests is to assure, by the appropriate acts and recitations, the functioning of the divine machine, so that it does not stop, so that the forces of the chaos always menacing at the periphery of the creation are repulsed, so that tomorrow morning the sun is born again from the horizon to dispense light and heat to men.
Worship is made before material representations of the god: innumerable statues, bas-reliefs and paintings, are there to materialise the god's presence.
The principle divine statue, the one which resided in the shrine of the temple, was however by its nature different from the others: it indeed contained the God'supresence, and therefore represented an idol in the true, while the other representations are icons. Therefore, at this level there exists a sort of hole in the otherwise insurmountable wall which separates the world of the gods from the one of men. One understands all the precautions taken around the statue therefore: if one struck a blow at it, it would be a sacrilege, with potentially terrifying consequences.

The gods also have the constant need that one recalls who they are, for why they are useful, and that one incites them to act.
The intermediary, the one who achieves the communication between the human world and the divine world, this is the Pharaoh. It is he who is represented as officiating on the walls of all the temples of Egypt. The priests are merely his delegates in this function.
Let's notice that, even though faith was certainly great in ancient Egypt, the ministerial function didn't imply in itself any personal adherence to the god that one served. It certainly didn't pose any problem to a priest of Amon in Karnak to serve Aton if the king, of whom he was the delegate, ordered it of him.

The Egyptian didn't like abstraction and couldn't imagine transcendence.
He needed a material support for his devotion. The same principle explains the profusion of these supports in royal tombs or those of private individuals.
In fact, according to the principles of sympathetic magic, all these representations exist and indeed are animated in the beyond, an absolutely different world in imagination of the Egyptian to the world which we discern. These parallel "worlds" are as "real" as one another. One could call them the sensitive and the perfect.
In the sensitive world, that of everyday, everything can exist, good or bad. On the other hand what the Egyptians represented on their monuments of eternity (temples, tombs), is an idealised imaginary world, a perfect world: the plants there are gigantic, abundant hunting and fishing, there are no grasshoppers or bad Nile which destroy the harvests bringing famine. Pharaoh defeats all his enemies there in an uninterrupted continuation of military victories. It is the triumphant world of the Ma'at.

The gods are many and everywhere in the Ancient Egypt. They are so involved in all the things of the life that the ancient Egyptians didn't have a word equivalent to our word "religion", since this supposes a dichotomy between profane life and sacred life.
The Egyptian religion is fundamentally polytheistic, and remains so until its disappearance.
To want to see ulterior monotheistic thoughts in the ministerial elite class while the people tend to be idolatrous, as has been proposed (for example by Drioton), don't rest on any convincing proof.
Certainly, one finds in the Egyptian texts with expressions of the type "nTr=j pw", "this, my god" in the singular, but they designate in fact the god of the nome, of the city, or the one which the supporter chose as his protective individual which is so obvious that it is not necessary no for him to name the god.
Also notice that we ignore almost everything of the real faith of the Egyptian, the popular religion. Nothing allows us to think that it differed fundamentally from the one of the clergy.

doesn't change this analysis. tried to simplify a religion which he judged to be too complex, but didn't want to suppress the divine forms. For example the name developed of his "unique" god Aton is in fact "Re-Horakhty-who-rejoices-in-the-horizon-under-the-name-of-Shu", and makes reference therefore to three divinities of the pantheon. It is certainly possible that the personal title the monarch felt his god was indeed unique, but nothing proves it.
In any case, this belief, being too different from tradition, never spread further than the king.

Unlike the open religions which offer theoretically only one truth, written in an immutable Book and to which the faithful one must adhere without restriction, in Egypt one finds a plurality of approaches of the divine one. None excludes the other, because none has the claim to be complete. Each one brings its vision which is added and never replaces the preceding one.
It indeed explains the reason why nothing of that which was once sacred one day must disappear completely: We construct a new temple on the foundations of another more ancient one of which we preserve the structures devoutly. We ramble on about the previous glosses of a sacred text, at the price sometimes of contradictions which seem to us incompatible. But which posed no problems to the Egyptian mind. We find a new explanation, or we leave the apparent contradiction.
So each city, every temple could have its creator god, different from the one of the neighbouring temple, without it affecting anyone.

The divinities of foreign origin could also be assimilated without problem, and see themselves endowing great cult centres, as was the case in the delta for divinities of Asian origin, such as Baal or Astarte.
There were no religious wars in ancient Egypt.
The Egyptians made steps toward the divine that was inherent and present everywhere in the sensitive world.
The effort was praiseworthy, but of the specific form which it took on in Egypt was still not understood by modern scholars for whom polytheism came along with a negative value of judgement.
Not even the Greeks, though polytheistic, and who gave us the major mythological writings which reached us. Not being insiders, the basics of Egyptian theology largely escaped them, from where the mockeries which one finds of Herodotus, or Diodore of Sicily, reproach for example the Egyptian love of gods with the head of a dog.
With their acquittal, in Egypt in a later period, which underwent multiple invasions, a tendency towards animal forms seemed to have developed itself, the upper levels of the religion remaining confined in the temples where the priests preserved intact the traditions.

On the whole, to approach the Egyptian gods supposes that we make an effort to erase as far as possible our own Judeo-Christian culture and our logical rationalisation. And that we do it with humility.
If we look at them with sympathy and try to feel them as much as to explain them, we have a chance of better understanding.

To go back to Bernhardt Lang: " (in polytheism)… mostly man is able to ally himself with the surrounding powers. He knows himself to be secure in the middle of benevolent forces. Here is what provides him with this sense of security, which is generally what is lacking to us, the man of today. They who understands the Gods can only to regret that their world is gone".

Paradoxically, it is the explosion of that which we tend to consider as Religion, embodied in general by the dogmatic monotheisms, and here by Christianity, which will sound the knell for the traditional religion of Ancient Egypt, of this natural religion which had even built in the Egyptian man into a social and political group with a length without equal in the history of the humanity.

Wether or not it is a spiritual progress is debattable.