An out-group is any group or category of people to which individuals feel they do not belong and with which they do not identify, often viewing them as different from or even in opposition to their own in-group. The distinction between in-groups and out-groups is fundamental to social identity theory and can influence social interactions, attitudes, and behaviours towards members of both groups. Individuals may perceive out-group members as less similar to themselves and may hold stereotypes or prejudices about them, sometimes leading to intergroup conflict or discrimination. The boundaries between in-groups and out-groups can be fluid and context-dependent, shifting based on social situations and group affiliations.