You will know if you go through it.

IME, it was a fully-conscious experience, and even though I don't remember too many details (it was 15 years ago), I still have pretty good memory of it, although it's mostly just impressions, as even at the time I wouldn't have been able to put it into words.

Basically, you lose a sense of dualism between "you" and everything else. "You" are everything, you are All. There is no sense of time, there is no "Here" vs "There"; everywhere is just Here, Now. It's an instinctual, familiar, visceral, Knowing-Feeling of just Being. It was simple, quiet, beautiful, and true.