Well, I had some doubts after reading one of the activities proposed in my course.
They told me to talk about social groups in my country, which would be Spain, in my case. I don't see it clear because I'm not quite sure if "social group" might be equivalent to the term "urban tribe", which we use here in Spain, but I don't know if it's a correct term in english.
I think "Urban tribe" is referred more to teenagers groups that have the deliberate intention of being classified by society. They want to be different and they dress like that, listen to specific music and have their own cliches... I think I'm already too old in my thirties to know much about this groups but I might be able to try. To name a few, I guess I can say in Spain there are "emos", "góticos", "punks" and "skinheads". But I'm not sure the last two still exist, at least they existed when I was younger :)
On the contrary, I understand "social group" as a term which refers to people that are classified based on his economic level, interests, and activities, but don't have the intention of being part of a specific group. As an example of that in here, I can only think of the "Single" trend. The marketing world dubbed this way people with no strings attached, who like to travel alone, taking care of themselves, ambitious, etc... particularly, I found it very funny. They even organize cruises for "singles", looks like an excuse to stop being one of them to me...
What do you say? Can you think of more social groups?