An airdrop is free tokens sent to hundreds or thousands of bitcoin wallet addresses. Developers use airdrops to promote new blockchain projects or services and to ensure a fair distribution of tokens when the project starts.
Crypto airdrops are usually safe, although there have been some pump and dump schemes and more severe scams. An airdrop does not compromise your wallet, and legitimate airdrops never request an investment or personal information. You have to pay income tax on airdrops because the IRS considers them to be income.