An official is someone who holds an office (function or mandate, regardless of whether it carries an actual working space with it) in an organization or government and participates in the exercise of authority (either their own or that of their superior or employer, public or legally private). The term officer is close to being a synonym, but it has more military connotations. An elected official is a person who is an official by virtue of an election.
Officials may also be appointed ex officio (by virtue of another office, often in a specified capacity, such as presiding, advisory, secretary). Some official positions may be inherited. A public official is an official of central or local government. A person who currently holds an office is referred to as an incumbent. Used as an adjective, something "official" refers to something endowed with governmental or other authoritative recognition or mandate, as in official language, official gazette, or official scorer.