A cache is a temporary storage area for instructions and data, usually implemented in high-speed memory. It is used to shorten data access times, reduce latency and improve input/output operations.
Because almost all application workload depends upon input/output operations, caching data improves application performance. It replicates information from slower storage or network resources to enable quicker access while using fewer resources than the original source.
For example, Web browsers such as Chrome, Firefox, Internet Explorer, Edge or Safari use browser caches to improve performance for frequently accessed webpages. While visiting a webpage, the files requested by the browser are stored locally in the browser cache. When re-visiting the page, most of the files can be retrieved from this cache instead of having to download them again. This is much faster and allows for a better user experience.