Bounty and airdrops are promotional activities to their ICOs,
✓ Like he said, Bounty is program to Promotes their ICO project. There is many ways to promotes like facebook, twitter, blog, etc. you just follow the rules and get paid.
✓ Airdrop is giveaway. More airdrop is scam maybe. But if you get airdrop, i think is just a bit amount.
if you are new in this forum, try for social media Bounty.
Good Luck