An expert systems is software that contains a knowledge base of facts and relationships and has the ability to make inferences based on that knowledge base. An experts system is a computer based information system in which knowledge is represented in data in which the processing of the knowledge is directed primarily by computer programs.

An experts system is a computer application that guides the performance of ill structured tasks which usually require experience and specialized knowledge( i, e, expertise) . using an expert systems non experts can achieve performance comparable to an expert in that particular problems domain. Experts systems can be considered an instance of a decision support system. The unique distinguishing feature of an expert system is the knowledge base the data and decision rules which represent the expertise.