Based on airdrop definition, it is when a blockchain project distributes free tokens or coins to the crypto community. To become a recepient of the crypto airdrop, the requirement is that you have coins from pertinent blockchain stored in your wallet. These airdrops needed a proof that you were the owner of BTC or ETH  at a certain time of the blockchain. Other airdrops require social media post or you need to contact a member of the team on bitcointalk forum.