Official cover is a term used in espionage

Espionage

Espionage or spying involves an individual obtaining information that is considered secret or confidential without the permission of the holder of the information. Espionage is inherently clandestine, lest the legitimate holder of the information change plans or take other countermeasures once it...

 to refer to operatives who assume positions in organizations with diplomatic ties to the government for which they work.

Official cover operatives are granted a set of governmental protections, and if caught in the act of espionage, they can request diplomatic protection

Diplomatic protection

In international law, diplomatic protection is a means for a State to take diplomatic and other action against another State on behalf of its national whose rights and interests have been injured by the other State...

 from their government. In other words, official cover operatives are agents officially recognized by their country. In contrast, non-official cover

Non-official cover

Non-official cover is a term used in espionage, particularly by national intelligence services, for agents or operatives who assume covert roles in organizations without ties to the government for which they work. Such agents or operatives are typically abbreviated in espionage lingo as a NOC...

(NOC) refers to operatives who assume positions with no ties to their government, and whose actions are officially disavowed by that government.