Followers are interested in what you tweet Karen, or at least we hope that's why they follow us lol :)
If you interact with them and tweet stuff that will interest them, (related to but not just your affiliate links) and get yourself noticed, you can make money when your followers there begin to buy from you, your affiliate links, or join your business programmes.
It doesn't happen overnight and it's one of the reasons that there's such a debate about how many followers you should aim to gain and how many people you should follow.
If you follow too many people with different interests, it's difficult to keep all their interests in mind and interact with them.
If you unfollow people who are following you, often these days they will be using automated software that will in turn unfollow you as well...