Any member (be they buyer, seller or both) can do a number of things that can be of interest to followers...eg people may like to follow your interests (more specifically, collections - not forgetting that old lists and saved searches are now part of your curated eBay "interests", whether public or private), if you follow a seller or someone who creates collections, their new listings / items added to collections will show up in the follower's home page, along with their own saved searches and interests.
It doesn't look like you've written any reviews or guide, but that's another reason a member may follow another (i.e. special interest reviews and guides).
