An Expert System is a computer program designed to mimic the decision-making abilities of a human expert in a specific field. These systems use a set of rules and knowledge bases to analyze information and provide solutions or recommendations. They are commonly used in areas like medicine, finance, and engineering, where expert knowledge is crucial for problem-solving. The core components of an expert system include a knowledge base, which contains facts and rules about the domain, and an inference engine that applies logical rules to the knowledge base to deduce new information. Examples of expert systems include MYCIN for diagnosing bacterial infections and DENDRAL for chemical analysis.