Knowledge-based and expert systems are AI-driven systems that simulate human expertise to solve complex problems in specific domains. These systems rely on a structured knowledge base, consisting of facts and rules, and an inference engine that applies logical reasoning to derive conclusions. Expert systems are widely used in fields such as healthcare, finance, and engineering, where they assist in decision-making, diagnostics, and problem-solving. They can incorporate machine learning and natural language processing to enhance their adaptability. While highly effective in specialized areas, these systems require continuous updating to remain accurate and relevant as knowledge evolves.