In this chapter solar cell physics is reviewed. The discussion starts with classification of solar cells. Solar cell operation is introduced in the context of the two essential processes in any solar cell, i.e. light absorption and charge separation. Various loss mechanisms including optical, recombination, and resistive losses in solar cells are discussed and their remedies are outlined. Parameters quantifying solar cell performance beyond cost and efficiency are introduced. The reader is assumed to have college-level solid-state physics or device physics knowledge.