What is airdrop?
Some ico's choose to do an airdrop, that means they give away some portion of their altcoin as a way of promotion. They do it for marketing reasons, it's not really a free lunch as some people may suggest. There is an old saying, when you don't pay for a product you are the product yourself.
An alternative to airdrops are bounties. A cryptocurrency bounty allows you to earn altcoins by doing some marketing related tasks. I think they are better than airdrops because you can earn more. Airdrops usually don't pay that much. Some bounties on the other hand pay big bucks but it depends on the work that you deliver. You get payed on a basis of performance so the better you perform the more you can charge.
I've wrote a post about cryptocurrency bounty hunting, you can read it here on steemit: