There are different types of crypto airdrops, but they usually consist of a small amount of cryptocurrency being distributed to several wallets (usually on Ethereum or Binance Smart Chain). Although less common, there are also projects that giveaway NFTs instead of regular crypto.
Some projects will do the distribution without asking for anything, while others will ask you to perform certain tasks before claiming. These tasks often include following social media accounts, subscribing to a newsletter, or holding a minimum amount of coins in your wallet. However, you are not always guaranteed to get the airdropped tokens.