A spirit guide is meant to advise you and lead you on your life path. These spirits are with everyone and are there for your own good and will never give you "bad" advice. Unfortunately most people cannot hear their guides. Many psychics are able to communicate with your guides for you and pass their messages onto you.
A spirit of an archetypal force or ancestor that works closely with an individual, keeping them safe and offering guidance. A spirit guide may be the spirit of a deceased relative, of an ancestor from many generations past, a force of nature, or a dweller in the celestial realms (such as angels, devas, gods, and goddesses).
A spiritual guide, who was someone you knew in a past life. Someone who is on the same spiritual level of knowledge as yourself to aid and guide an individual through the higher purpose or mission of their life in this embodiment.
A spiritual entity who provides information of "guidance," often through a medium or channeled. The spirit provides guidance only after the channeled relinquishes his perceptual and cognitive capacities into its control.
"Spirit guide" is a term used by the Western tradition of Spiritualist Churches, mediums and psychics to describe an entity that remains a disincarnate spirit in order to act as a spiritual counsellor or protector to a living incarnated human being.