This document discusses social groups and processes. It defines social groups as collections of humans brought together through social relationships and common goals. Groups are classified based on size, structure, type of contact between members, and other factors. Primary groups are small, stable, and involve direct, face-to-face contact between members. Secondary groups are larger and involve more impersonal, indirect contact. An in-group is the group an individual identifies with, while an out-group is any other group. Crowds are temporary gatherings of many people brought together in close proximity around a common focus.