What is a social group and why are they important to society? what are two groups that you are a part of?

A social group is any group of people that interacts socially - socially just means here "with others". 

Some social groups are small - friends - and some are really big - a nation. 

They are important to society, because in a way they are the society itself - its different parts. It forms the basis for the society's interactions, for example the raising of children happens within a family - which is a social group. 

You are part of many social groups, for example: your family, your classroom,your school and your nation