how the social sites store the user, user's related posts and comments on the posts [closed]

can somebody please explain how social site db works, how the user is stored in the database, how the friend request or follow system works, how the posts by the user and the comments on the by other users and how they are shown on the web page, like Facebook the user registers the account sends the friend request, post something and the friend comments on the post how this is done and how what structure is used in db. thank you<3