As someone who never played the older games (except for when I was 6 at a friend's house) how do the what if's work? how far do they each go and how does making your own work?

Cause like I just saw a "what if goku survived after beating raditz" and I'm wondering how far does that go, til like the end of that arc or what? Cause it'd be sick if you could go til the end/most recent with that.

Sorry if yall don't know either I'm just new to the concept of the what-if system.