This chapter provides a thorough and comprehensible overview of epilepsy and genetics. The identification of epilepsy genes can contribute in many more important ways to public and individual health. In order to understand the genetic causes of epilepsy, it is important to review a few basic concepts and definitions. The chapter explains the basic genetic terms and concepts such as genes, chromosomes, autosomal dominant disease, autosomal recessive genes, sex chromosomes, X-linked dominant disease, and X-linked recessive disease. It explores how epilepsy is inherited. The risk of developing epilepsy in the relatives of affected people is increased compared with the general population, but the size of this risk depends on many factors, one of which is closeness of the relationship to the affected person. Studying the families of people affected with epilepsy is an important way of investigating the genetic contributions to the development of epilepsy.