A bounty program, an airdrop, a campaign,... are sometime the same method or not for free token distribution. A bounty usually request to follow fb group, twitter, reddit, YT channel, Telegram,... Generally, it's very good way to earn free tokens. You can find the bounty program through the bitcointalk forum and many different social forums...
But now there are too many fraudulent ICO projects all over the Crypto market. Therefore, it is not easy to earn free tokens if we choose the wrong campaign. Please check carefully before participating in them. It may take time and effort.