The document introduces artificial immune systems (AIS), which are computational systems inspired by the human immune system. It provides an overview of the immune system and its properties such as diversity, learning, memory, pattern recognition, and self/non-self discrimination. These properties provide a biological paradigm for developing AIS algorithms. The document then discusses representation schemes, affinity measures, and generic algorithms that have been developed for AIS, including negative selection, clonal selection, and immune network models. Finally, it reviews applications of AIS and discusses current trends in the field.