Generally, Fan is a one-side following, and Friend is a mutual one. Anyone can Fan follow you freely, but a Friend follow would request your acceptance and if you accept it you would follow they back as a Friend automatically.
But if you Fan followed someone and they Fan followed you back, you won't be Friends automatically.

Fan will get to see what you post publicly, and Friend can see what you post both publicly and privately if you choose to. You can also choose to share a post with any Friend you want to include.

amesi0801: I got it, Thank you so much!