All those terms refer to the same phenomenon, to which different people gave different subjective interpretations. You basically focus your attention into a non-physical realm. You can focus into a reality created by your own imagination, or into in a reality in which there are other participants too.
Everything expressed here is what I believe. Keep that in mind when you read my post, as I kept it in mind when I wrote it. I don't parrot others. Most of my spiritual beliefs come from direct channeling guidance. I have no interest in arguing whose belief is right, and whose is wrong. I'm here just to express my opinions, and read about others'.