Internet browsers often store copies of visited web pages, images or sounds on your local hard drive. The pages, images and sounds are part of your Temporary Internet files and are often referred to as cache. Cached pages can make browsing the web quicker because your computer can get some or all of a web page from your computer instead of the Internet.
However, when some or all of a web page is retrieved from cache, you may not see updated content on the page because your cached information may only show you what you saw on your last visit, depending on your Settings for Temporary Internet files. Also, cached information on your hard drive does take disk space. For these reasons, it's helpful to clear your cache from time-to-time.