Authority (Derived from the Latin word auctoritas) can be used to mean power given by the state (in the form of government, judges, police officers, etc.) or by academic knowledge of an area (someone can be an authority on a subject).
When the word Authority is used in the name of an organization, this name usually refers to the governing body upon which such authority is vested; for example, the Puerto Rico Electric Power Authority or the Massachusetts Bay Transportation Authority. It is also the permission to act.
Adapted from Wikipedia