Cache is a small data-memory storage area in your computer. Browsers use cache to maintain copies of files or pages you have already downloaded so you don't have to do so each time you access them online.
A cache server (cache engine) is a server relatively close to Internet users that saves (aka, caches) Web pages—and possibly FTP and other files—that all server users have requested. The cache can then satisfy future requests for these pages, rather than requiring the use of the Internet.
A cache server not only serves its users by getting more information more quickly; it reduces Internet traffic.