Same angle grinder tool, just a different wheel instead of the cutting or sanding wheel.
When you get the flap discs, get the adapter as well, it gets the wheel out away from the grinder more to get into tight spaces. And remove the shield / guard from the grinder as well.
Here's a stock photo of some discs. I usually use the 60 grit, but it comes in a finer 80 grit and rougher 40 grit as well.
View attachment 99519
Here's a vid where this guy uses an extra lock nut to extend the range of your disc (surface area covered) and still able to use the guard.
Thanks on the flap disc tip! Made a world of difference.