An alicorn is a little pony with the characteristics of an earth pony, pegasus, and unicorn simultaneously, as well as possessing unique emergent magical characteristics arising from the interaction of these three pony types. As a result, some alicorns have unique talents and magical abilities not readily available to any other pony type. Alicorns are naturally biologically immortal; other pony types are not. Alicorns may be natural-born as a result of their genetics, or may be born as other pony types and later "ascend" to become an alicorn.
Partly due to the historical rarity of both alicorns and pegacorns, there is sometimes confusion in the distinction between an alicorn and a pegacorn (which a few pegacorns have tried to encourage in order to take personal or political advantage of the traditional association of alicorns with divine or royal status).
Known historical alicorns include:
The Golden Age princesses Cadence and Flurry Heart presented themselves as alicorns, and bolstered this with skillful life extension magic allowing them to seem superficially ageless for centuries, but were in fact pegacorns. Queen Meridian of New Equestria claimed to be an alicorn, but it was believed in the years after her death that she was probably a pegacorn.