A cache is a small, high-speed storage area that temporarily holds frequently accessed data to improve performance. It allows systems, such as computers and web browsers, to retrieve information quickly without needing to access slower storage options like hard drives or remote servers. Caches can be found in various forms, including CPU caches in processors and browser caches in web applications. By storing copies of data that are often used, caches reduce latency and enhance the overall efficiency of data retrieval, leading to faster response times for users.