In-group and out-group

An in-group is a group of people or things that share qualities. For example, people who are the same age are in the same in-group. An out-group, on the other hand, is a group of people or things that do not share qualities. For example, people who are a different age are part of a different out-group. People often prefer their in-group over the out-group because they think they know more about the members of the in-group.