This is sociology but could someone ..i need an example of what they mean by this
make a list of groups to which you currently belong, and then organize the list by the type of group. now, make a list of groups to which you belonged during elementary school. why have your group memberships changed as you've grown older?
just give me a few examples of groups..

Examples of primary groups are families, friends, peers, neighbors, classmates, sororities, fraternities, and church members. These groups are marked by primary relationships in which communication is informal. Members of primary groups have strong emotional ties. They also relate to one another as whole and unique individuals. 
In contrast, secondary groups are those in which individuals do not interact much. Members of secondary groups are less personal or emotional than those of primary groups. These groups are marked by secondary relationships in which communication is formal. Members of secondary groups may not know each other or have much face‐to‐face interaction. They tend to relate to others only in particular roles and for practical reasons. An example of a secondary relationship is that of a stockbroker and her clients. The stockbroker likely relates to her clients in terms of business only. She probably will not socialize with her clients or hug them.