I have accounts on Stack Overflow and Ask Ubuntu and they cover almost all my queries. I just joined Super User, and I want to know which topics are supported and which types of questions are asked in this community.
Well amongst other things, we predate AU, and our scope was meant to compliment SO's programming centric viewpoint.
Clearly you're a programmer, who uses ubuntu. There's people with non programming questions to do with computers who may or may not use ubuntu. Or might be ewoks. Many hardware questions are on topic here, and we have a broader tho overlapping scope with many of the newer sites, the young whippersnappers.
That said, our tour and help pages go into our scope in detail, and its all there.