Like I said, read the documentation to see what all this mod can do and you won’t be sorry you did. It can control your Sim’s pregnancies, edit just about every aspect of your Sim down to their active buffs (what emotions they’re feeling), and even slow down time. Needles to say, you can do a lot with this mod.
It’s best to read the documentation on the website fully and/or go through all the options in-game to see what they all do. One word of caution though, this mod is huge and has a ton of options. while you’re controlling your family of Sims.
Story progression means that the Sims you don’t control directly (NPCs or other families you’ve created but you aren’t actively playing with at the moment) will continue to live out their lives, move between houses, get married, have kids, etc. It is a master controller mod that allows you control over just about every aspect of gameplay plus it allows for story progression. This mod is huge and almost what I’d consider “all encompassing”.