Different people have different ideas about it. I spent a lot of time studying David Hawkins, he spoke of 5 levels of enlightenment. You start with finding total peace with yourself and progressively shed more and more aspects of self and ego that still remain until you’re at the absolute pinnacle. This doesn’t happen very often and according to him it’s only happened 5 times.
I do not frame my own beliefs according to Hawkins, though we do have some things in common. Both of us understand enlightenment as a multi-lifetime evolution. But where he understood spiritual evolution as fitting on a quantifiable scale, I find that such a thing could never appreciate the full depth of what it means to be human.
Accordingly, I group enlightened beings in two categories. Those that are ‘emerging’, and those who are ‘fully-formed’. Emerging beings are typically born unenlightened and then eventually have an “enlightenment event” sometime in their lives. Most of our spiritual teachers belong to this category, though many of them aren’t and are instead unenlightened beings who are preying on the weak and insecure.
Emerging enlightened beings have many lifetimes in which their path is to experience enlightenment so that they can better deal with it and understand it.
The ‘fully-formed’ enlightened do not think enlightenment is special and so have no desire to teach it. I do not follow the Buddhists in thinking that enlightenment is the end of the human journey. Enlightenment makes it difficult to be human, but by no means impossible.
I have investigated teaching what I know and the realization that I came to was that consciousness growth can not be meaningfully accelerated. Even if you made someone enlightened in this life, they probably wouldn’t be able to handle it and it really isn’t worth it. People become enlightened when they’re good and ready for it.