What is dissociation?

[Dalfir]

I'm not sure where else to post this. I understand that hallucinogens are three broad categories. Psychedelics, which allow information and signals that would previously be filtered by the brain to reach the concious mind, dissociatives and deleriants.

What do dissociatives do? Are they the opposite of psychedelics in that they don't amplify signals travelling to the concious mind, but rather block them out so that some senses just aren't present? Before I got an interest in hallucinogens, I got high off N20 which, for about 15 seconds, sent me into a total trance where no influence of the outisde world had any effect on me. Do dissociatives just allow the concious and subconcious to function, while all outside sensations are blocked out?

I've heard that deliriants can cause true hallucinations, but compared to dissociative and psychedelics, what do these do?