Saving user data?

Over the last 5 years, I've taken a lot of game development courses (mostly on Unreal Engine and a few on Unity). NONE of them have explained about saving user data to a server (or however game development handles it). I'm an experienced web developer (websites) and this seems to be a much different process.

Usually in tutorials I see, "Game Over", "You Win", "You Lose". Occasionally, it might save user data locally and "save" the user's points.

Can someone guide me to a course/tutorial/creator kit that explains how the servers or saving user data/creating register/login systems work?