Following just means that buyers or sellers like your pieces and are informed of when new items are posted, it's a good thing :o)
Favouriting is when someone likes your item and adds it to a collection of other items they like, maybe to go back to to purchase at some point or just simply because they think it's nice, again a very good thing.
A secret admirer is just someone who has favourited who keeps there favourite items for only them to see. Some people do this, but i think it's best to keep them open to the public so others can see them and possibly buy or favourite them :o)
Hope that helps and don't worry there is no creepiness involved .