nginx [engine x] is a HTTP server and mail proxy server written by Igor Sysoev.
Rack::Cache is a component to enable HTTP caching for Rack-based applications such as Rails.
Allows a website to define how a page is rendered in Internet Explorer 8, allowing a website to decide to use IE7 style rendering over IE8 rendering.
UTF-8 (8-bit UCS/Unicode Transformation Format) is a variable-length character encoding for Unicode. It is the preferred encoding for web pages.