This document provides an introduction and overview of the epidemiology course PH250B Epidemiologic Methods II. It begins with definitions of epidemiology and key epidemiological terms. Epidemiology is defined as the study of the distribution and determinants of health-related states and events in populations. Examples of distributions of health, such as rates of breast cancer and obesity, are shown. Determinants of health according to the WHO and Healthy People 2010 initiative are discussed. The document then discusses how epidemiological questions can address causes of cases or causes of incidence. It provides examples showing how the same exposure may provide different answers depending on the question asked. Health paradigms are discussed as shaping epidemiology and vice versa.