The function of a caching system in web applications is to enhance performance by storing frequently accessed data closer to the user. Caching minimizes the need to repeatedly fetch data from the original source, significantly reducing latency and improving load times. By temporarily storing responses from databases, APIs, or web pages, caching systems enable applications to serve content to users more efficiently. This optimization is crucial for delivering a smooth user experience, particularly for high-traffic websites and applications that require fast response times.