Scammers announce a fake token airdrop, often impersonating a real, popular project, and direct people to a "claim" website that looks legitimate but is entirely under the scammer's control.
The site prompts you to connect your wallet and sign a transaction to "claim" the free tokens. Instead of granting you tokens, the transaction actually grants the scammer's contract permission to move assets out of your wallet — sometimes immediately, sometimes at a later time of their choosing.
Some variants skip the technical approach entirely and simply ask you to enter your seed phrase directly to "verify eligibility", which is an even more direct route to losing everything in the wallet.