Airdrop is a easy way to earn free crypto. Some new cryptocurrencies giving free tokens for people as a part of their promoting campaign. Basically you need to sign up their website or fill some form and do some easy tasks like following their twitter or join to their telegram channel. If you have some luck you can earn good money but some crypto experts saying these days 90% of airdrops are scams so try to earn with airdrops if you don't have money to invest or if you don't like to take risk.