Literally ripped out of reality. Teleported to another time and place. It totally disrupts your senses from reality, and substitutes something else. One time I recall seeing the walls growing with vines like snakes, and being transported to a place with purple light.
When you emerge, you feel refreshed and renewed.
Do you remember deep dream? When i first saw it, I thought we might have some kind of ML model of the human experience of D.