A I R D R O P:

A marketing campaign that distributes a specific cryptocurrency or token to an audience.

It is usually initiated by the creator of a cryptocurrency in order to encourage use and build popularity of the coin or token. Most airdrop campaigns run with mechanics such as receiving coins or tokens in exchange for simple tasks like sharing news, referring friends, or downloading an app.

Also read: https://en.wikipedia.org/wiki/Airdrop_(cryptocurrency)