what is the browser cache?

[sukishan]

what is the browser cache?
A web browser stores objects—for example, images, HTML documents, style sheets—downloaded over the network in a special area called the browser cache. The way the cache works is simple: when the user navigates to a page, the web browser will first check if the browser cache already contains the content for that page. If the content is still fresh in the cache, another download is unnecessary. Easy, right?

What may be news to you is that the HTTP/1.1 protocol—the communications protocol in common use on the Web—allows you to specify what content is cacheable, and for how long the downloaded content can be considered fresh by the browser cache. This information is specified in the response headers returned by the web server. Response headers are lines of text describing the page being sent (and the server that's sending it). You can actually view this information if you're using the Firefox browser and have the Live HTTP Headers extension installed.

The parts of the response header relating to cache control are, not surprisingly, called the cache control directives.