Out of body experience

An out-of-body experience (OBE/OOBE or simply projection) is an event in which one's consciousness, either in whole or in part, leaves the physical body but retains its ability to sense things. Such extra-sensory perceptions are typically interpreted as images from the physical world or another plane of existence.

Planes
Though beliefs necessarily vary, some of the common planes that are reported to have been visited include:
 * The physical plane (remote viewing)
 * The Astral (astral projection)
 * Dream worlds (lucid dreaming)

Sleep paralysis, involved in some methods of projecting consciousness, is the paralysis of the physical body. Though this is a common method, projection does not require a sleeping or otherwise paralytic state.

Boundaries
Due to the poorly understood nature of consciousness, the boundary between distinct planes is not readily expressed in physical terms and is often poorly understood. One bounded by materialist philosophy, for example, might hold that experiences of lucid dreaming or sleep paralysis are sufficient explanation for claims of astral projection. In other philosophies, though lucid dreaming can lead to astral projection, the world within the lucid dream is considered to be internal, while the astral is, by definition, external.