Airdrop
Free tokens given to early users of a protocol.
A project distributes its new tokens to people who previously used its smart contracts (testnets, swaps, bridges). Goal: build a decentralized community and reward early testers. Biggest historical airdrops: Uniswap (UNI 2020, ~$1200/wallet avg), Arbitrum (ARB 2023), Jito (JTO Solana 2023, ~$4000 avg). Airdrop hunting is now its own profession (sybil farming).
In plain words
A project gives its fresh tokens to wallets that previously used its services, such as swapping on the DEX or depositing to the bridge. It's a reward for early testing and a way to spread supply. You can get tens to thousands of dollars for nothing, but you must use protocols BEFORE they announce the airdrop.
Example
Uniswap UNI 2020: every address that swapped before September got 400 UNI = $1200 then, $17000 in 2021.