I'm not completely unaware what Initiation is but I'm not completely aware what it is as well. Most times Initiation itself seems to be an attainment of a certain level, Basically you have mastered the lower level and are now begining on the new one. Often it's said that with attainment people also achieve abilities (some things as simple as thought control, then to things more complex to such as Clairsentience (ie. Psychisim).
To make a game analogy (Despite knowing some people will cringe, Mwahaha), initiation is when you unlock a new level after mastering the previous level, this new level also has new weapons (abilities) which you acquire but at first don't entirely understand how to use them perfectly. It also of course has new enemies/tasks (challenges) that you have to overcome.
Thats the little of what I know of Initiation but this thread wasn't started to state what I know (as fact or as fiction) tp all you advanced (and not so advanced) magi but so you could share such information with myself and see If I'm mis-stepping anywhere in my understanding.
As for understanding, I do realise initation is possibly one of those aspects of that occult can't be thorougly understood until experienced for oneself.