To put it simply, an airdrop is what you could call a give-away of coins/tokens in exchange for a small effort. This means that if you store your coins in a certain wallet or hold a certain coin you will get another coin/token deposited in your wallet for free.
Thats sounds sooooooooooooooo shady. Whole this ICO stuff which then build another scam layers on top of it should ended long time ago. Even google banned crypto adds because of ICO's ongoing scams :/.
Just stop, use crypto, dont mess with layers of bad things on top of it.