If someone follows you on Facebook, that means that they are following your updates, posts and they will get to see your activity in their News Feed.
When you are friends with someone, they automatically follow you. However, people who aren’t your friends can also follow you – depending on the privacy settings you have on. In your Settings, you can change these options from either Friends or Public. You can also change who can comment on your public posts, share them or react to them as well.
To see who’s following you, you can either turn on notifications for when people follow you or interact with your public posts or you can find out who’s already followed you by going to the Friend’s tab on your profile, click on More and select Followers from the drop down menu, it’s quite simple!
On the other hand, to follow people on Facebook you can just go to their profile and click on the follow icon!
After following someone, you can choose how often or where you will be seeing the posts. When you select the See First option, you will see this at the top of your News Feed much more often. This is the same for Facebook Pages that you like, so you can prioritize which ones you want to see first! There is a limit though to how many people you can See First, so make sure to choose wisely.