A production system (or production rules system) is a computer program typically used to provide some form of artificial intelligence, which consists mainly of a set of rules about behavior. These rules, called productions, are a basic representation that is useful in automated planning, expert systems, and stock selection. A production system provides the mechanism necessary to execute productions in order to achieve some goal for the system.
Productions consist of two parts: a sensory precondition (or "IF" statement) and an action (or "THEN"). If the precondition of a production coincides with the current state of the world, then production is said to be triggered. If you execute the action of a production, it is said that it fired. A production system also contains a database, sometimes called working memory, which maintains data about the current state or knowledge, and a rule interpreter. The rule interpreter must provide a mechanism for prioritizing productions when more than one is triggered.