A CACHE file stores recently used information in a disk cache for a specific program. It is used by web browsers, image editing programs, and other applications to speed up the loading of recently viewed data.
CACHE files may store different types of information. The most common types are browser, memory, disk, and processor cache.
Caching is done in the background of applications and CACHE files are referenced by applications, which means you will most likely never encounter CACHE files. They are not meant to be opened manually but some cache files can become rather large and may be deleted to free up disk space.