This document provides an overview of sociological concepts related to society and social groups. It discusses key thinkers like Durkheim, Marx, and Weber and their theories on what holds societies together. It describes the evolution of societies from pre-industrial to industrial to post-industrial. Pre-industrial societies included hunter-gatherer, pastoral, horticultural, agricultural, and feudal structures. Industrialization led to urbanization and new social classes. Post-industrial societies are based on information and services. Functionalism examines how society's elements interconnect, while conflict theory sees society as competition over resources between social classes.