Hi! Welcome Back!
It would be very helpful if you could tell us what type of information you are interested in refreshing. Since there are so many ways to play this game, we'll need a little nudge in the right direction. Of course, here are the links to a few starter/info/help sites for both modded and unmodded play. I am certain you already know of them but they are great places to re-introduce yourself to the game.
Happy Simming!
https://www.carls-sims-3-guide.com/
https://sims.fandom.com/wiki/The_Sims_3
https://www.nraas.net/community/home
https://modthesims.info/
EDIT:
Just thought of this. You could also check this thread right here on the forums for some refreshers or to learn something new! It started back in 2017 so it's quite long. ;)
https://forums.thesims.com/en_US/discussion/917439/sims-3-things-you-didnt-know/p1
