In some of the threads I'm following lots of users mention the word "bounty campaign" or "bounty manager" which is a term I've never heard before. Is it something similar to a marketing campaign?
Yes, you hit it right its a form of a marketing campaign, and usually, from start-up projects, they need people to spread the word about their project and advertise it on social media, forums, and blog sites so that many potential investors will come in to buy its token offerings. While the bounty manager is a person who has the responsibility to check all of the marketing campaigns (bounty campaign) that he was managing, that's the simple explanation about it.