Varnish is a web accelerator platform, which caches content for faster access. It’s sometimes called a caching HTTP reverse proxy too and it works between a web server and a browser. When a site visitor opens a specific web page, its content is requested by the browser, and then the web server processes this browser request and delivers the requested content. If Varnish is activated for a website, it will cache its pages on the very first request and if the visitor opens a cached page once again, the information will be delivered by the accelerator platform and not by the web server. The improved speed is an end result of the considerably faster response speed that the Varnish platform offers compared to any web server software. Of course, this does not mean that the site visitors will keep seeing the very same content over and over again, since any modification on any of the web pages is reflected in the content that the Varnish platform keeps in its system memory.