A plane of existence is one of the many realities that exist in the Dungeons & Dragons multiverse. Sometimes called other dimensions, these realities may be accessed by spells, spell-like abilities, magic items, or specific creatures, and some of the more outlandish creatures are in fact visitors from other planes.
The differences between planes of existence vary, with some planes nearly identical and others quite alien. The "normal" world is part of a material plane, and each resident of a material plane calls their home plane the Prime Material Plane, while regarding other material planes as "alternate history". Among the more alien planes are the inner planes, which embody various forces of nature and from which elementals originate. More outlandish are the outer planes, home to numerous powerful beings, usually including the deities of the multiverse. Connecting these planes are the insubstantial Astral and Ethereal Planes, which are sometimes used for rapid, yet dangerous, transportation between (or sometimes within) planes.
See also: Category:Planes of existence