A Practical Guide to Varnish
devblog.factual.com/practical-guide-to-varnish
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Varnish is an open source, high performance http accelerator that sits in front of a web stack and caches pages. This caching layer is very configurable and can be used for both static and dynamic content.