The storage of Web files for later re-use at a point more quickly accessed by the end user.
Caching can happen at many places, including proxies (i.e. the user’s ISP) and the user’s local machine. The objective is to make efficient use of resources and speed the delivery of content to the end user.
While caching can have a positive impact on the user’s experience, it can have a negative impact for site publishers, resulting in undercounts of page views and ad impressions. In response to this problem, sites have implemented various cache-busting techniques to better ensure that all performance statistics are accurately measured.
see also: Digital Marketing Tools