How does a buyer become a fan and how does the seller know that they have a fan
and what exactly does it mean for the seller?
Any help would be great thanks
You can use this page, generically: https://www.bricklink.com/pref_favorite.asp
or specifically by clicking Fans in the upper right corner of a given
store. It’s there, you as seller “know that they have a fan” You have two.
As to what it means: not much, other than being able to send blind announcement
emails to those that are fans. Blind, as they are anonymous to the seller.