Welcome to bitcointalk community. This is the best place to learn about the crypto world and there are too many ways to learn about cryptocurrency. Because Google is your best friend. Airdrops mean an ICO project giving free tokens to limited participants for small tasks. The tasks are different with campaign by campaign. Normally they ask retweet, share etc. After that, you have to fill a google form with those details and your wallet information. After the ICO you will receive the tokens to your wallet.