From iA wiki
A store of goods or valuables concealed in a hiding place. A local pool of reserve goods or resources for use at specific times or when certain conditions are met. Most web browsers have 'caches to speed access to the web. Google has a large cache of web pages that its search engine is able to store.
In computers and programming, a temporary storage used to hold frequently accessed data in order to provide faster retrieval. There are various replacement algorithms for items in a cache, including FIFO, LRU, and clock.
An operating system generally keeps a cache of most frequently accessed memory, and often has a smaller, faster cache of the most frequently accessed items from the first cache. An example of a larger cache is a computer's RAM, that can cache large amounts of data from a hard drive, which reduces strain on the limited-life (and very slow) drive. Many servers have a great excess of RAM in order to allow for more user connections or to cache very large amounts of data, thus allowing faster access to data than a conventional desktop computer.