Board Thread:Questions and Answers/@comment-120.148.26.252-20130808102518/@comment-24278615-20131212060557

They are both the same. There is a function on Bilibili which allows you to subscribe to someone secretly. 这些人关注了Ta are those people who subscribed to someone publicly, and 粉丝 is the total number of subsribers.

People with 10k+ fans are known by almost everyone on Bilibili.