Enlightenment and salvation (liberation) are the same. Other words for it are Nirvana and Moksha. It’s a state of complete cessation of all suffering, absolute peace and serenity. There is no identity in enlightenment whatsoever, but it doesn’t mean that one loses its bodily sense of self. There is no bliss anymore, just emptiness, peace, the all-prevailing suchness of life. It is what it is, whatever it is, all the time. One acts, but there’s not even a slightest hint of emotional discomfort in all situations. Emotionally speaking, one becomes like a stone - invulnerable.

Self-realization is not a state, but rather an event. It happens when the ego gives up and admits its own non-existence. Before self-realization it’s impossible to know what ego actually is. In self-realization the ego is seen for the first time. The sense of identity permanently shifts from ego to the totality of experience. Self-realization is not the end of suffering, because ego cannot completely dissolve in one instant. But once discovered, it cannot be unseen. Self-realization can bring unimaginable bliss, which is a relative experience - it’s just freedom from suffering associated with identification with the ego. After self-realization people usually become extremely sensitive, very emotional, vulnerable, overwhelmed with the beauty of existence and compassion for humanity.

Most authors (for example, Osho, Jed McKenna) don’t make much of a distinction, and when they speak about their moment of enlightenment they’re actually talking about their moment of self-realization. This makes sense - no effort is required after self-realization, and even though it can take multiple years from self-realization to enlightenment, the process is usually irreversible and takes place on its own. Self-realization is a tremendous event, it feels like death. Enlightenment is the completion of this death process, and it doesn’t really feel much like anything - it’s very hard to say when the process is complete, which does not mean it is never complete.

What people refer to as “awakening” is usually seeing into one’s true nature, which is gaining an insight that there is such a thing as ego, it’s not real, and there’s something more beyond it. Some authors whose process was relatively slow (for example, Adyashanti) don’t make much of a distinction between “awakening” and self-realization, and prefer to call self-realization “abiding awareness” (whereas in awakening awareness could still be “non-abiding”). After awakening people can become very sensitive and emotional, but it’s very modest compared to self-realization and subsides relatively quickly. The idea that enlightenment is an infinite process which is never complete usually comes from this stage.

Let me give you an analogy:

Imagine a big pile of woods which you’re trying to set on fire, and it’s a challenging process. You use some kindling and it looks like it took on in one place. This is awakening. Chances are, it will probably fizzle out, and you’ll have to light it again somewhere. While it’s burning, you experience emotional pain, tears etc. You might have to try and light it multiple times. Every time it gets somewhat easier because the little fire from the last time dried the woods somewhat (which is to say, people become more in touch with their emotions after awakening, they start to feel things more deeply).

But then, one moment it really takes on. Something happens, and it just kinda explodes. Now there’s fire everywhere and there’s absolutely no doubt that it will not fizzle out - every piece of wood in the pile will burn. You have finally managed to start a fire, for real this time. This is self-realization. It makes the depth of emotion you experienced before look like child play.

Enlightenment is when everything burns and the fire is completely out. The coals aren’t even warm. This is not a moment per se, it’s pretty much a non-event. But nevertheless, it is bound to happen and it does happen.

P.S. Omniscience (“the state of knowing everything”) is a confusing term. The state of knowing everything is also the state of knowing nothing. You could say it’s a state of knowing everything about oneself while knowing nothing about the future. Knowing everything about oneself means knowing everything about human psychology, human behavior and the source of all human suffering, but it’s not the same as knowing everything about the Universe - the Universe is unknowable.