Social groups can be defined as collections of individuals who interact regularly based on shared interests and develop a sense of belonging. There are several types of social groups including primary groups with close personal ties, secondary groups with weaker ties, and reference groups that individuals compare themselves to. Group size and dynamics also impact member interactions, with small groups like dyads and triads allowing more intense engagement than larger groups. Networks of relationships outside established groups are also important to consider. Leadership, power differentials, conformity pressures, and obedience are key concepts in understanding group processes and influences.