An airdrop is a campaign that usually requires several social media steps like:
- Telegram group or channel follow
- Twitter actions such as like and retweet plus tag friends
- submit a form with some data.
In exchange, your address is added to a list that later is validated to check if all the requirements are satisfied to receive some free tokens.
Some airdrops have as prerequisites being owner of another cryptocurrency or to perform additional steps like community activity in the chats, etc.