Astral projection is the act of separating ones consciousness (perhaps their spirit) from their body, and traveling through a different realm. This realm is said to be the "astral plane", and in the astral you can find many interesting creatures and things to interact with.

Astral projection is perhaps similar to or the same as the journeying techniques used by Shamanic pracitioners throughout the ages.

This book offers a good introduction to Astral Projection. Included are step-by-step instructions for a method of achieving this state.