An airdrop is the act of sending tokens to wallets with the main aim of promoting awareness of a product. They are typically sent to an address as a reward for interacting with their product prior to a snapshot being taken. Some airdrops require the user to claim them. The reason for this is it can be cost-prohibitive from a gas standpoint to airdrop to so many addresses, so a claim function shifts that cost on the claimers.
Examples of previous airdrops
Accounts that had over 3 ETH volume on the NFT platform OpenSea between June 16, 2021, and Dec 16, 2021 were eligible for the LooksRare airdrop. Depending on how much volume a wallet had, it would receive different amounts of $LOOKS. Users had to visit the LooksRare website and claim their $LOOKS, which they could then sell or keep. The LooksRare airdrop was only claimable for a total of 10 days, ending on March 18th, 2022.
Ethereum Name Service
On Nov 8, 2021 the ENS governance token $ENS launched and people were eligible to claim their $ENS tokens. If you owned an ENS domain on or before October 31, 2021 when the snapshot was taken, you were eligible to claim $ENS tokens based on the formula calculated on the history of your wallet address. The amount of $ENS in which you could claim were based on the age of your .eth address, how long left you have left on your .eth address, and if you set your .eth address as primary ENS.
On February 11, 2022 the CoW Protocol Medium released information about the vCOW governance token. Starting off as non-transferrable, it would be up to CowDAO members to make the token transferring using the governance structure. Any user who earned a CoW-POAP, traded on either Ethereum or Gnosis Chain, and GNO holders were able to claim vCOW.