When creating a new post, you’re able to select who sees that post. You can create your own groups of friends easily by going here on desktop/laptop:
https://www.facebook.com/bookmarks/lists
If you’re on mobile, click on the 3 bars at the bottom for a menu of all your settings, then go to Friends List.
If you’re iOS, this feature has apparently been removed and you need to use a desktop/laptop to edit your Friends List.
