Age HTTP Header - Original Server Response

   The Age header contains the time in seconds the object has been in a proxy cache.

Must Revalidate HTTP Cache-Control

   Indicates that once a resource has become stale (e.g. max-age has expired), a cache must not use the response to satisfy subsequent requests for this resource without successful validation on the origin server.

X-Cache HTTP Header

   The resource was not in the website cache, and was pulled from the origin server like Varnish servers.

Vary Header Accept-Encoding

   The Accept-Encoding request HTTP header advertises which content encoding, usually a compression algorithm, the client is able to understand. Using content negotiation, the server selects one of the proposals, uses it and informs the client of its choice with the Content-Encoding response header.

Character Encoding :utf-8

   This website is using utf-8 character encoding in HTML , character encoding is used to represent a repertoire of characters by some kind of encoding system.

SPF

   The Sender Policy Framework (SPF) is an email-authentication technique which is used to prevent spammers from sending messages on behalf of your domain. With SPF an organisation can publish authorized mail servers.

PHP 5.4.45-0+deb7u14

   PHP: Hypertext Preprocessor is a general-purpose programming language originally designed for web development.

Varnish

   Varnish is an HTTP accelerator designed for content-heavy dynamic web sites as well as APIs. In contrast to other web accelerators, such as Squid, which began life as a client-side cache, or Apache and nginx, which are primarily origin servers, Varnish was designed as an HTTP accelerator.

Google Analytics

   Google Analytics is a web analytics service offered by Google that tracks and reports website traffic, currently as a platform inside the Google Marketing Platform brand.

Google Plus

   Google+ was an Internet-based social network owned and operated by Google. The network was launched on June 28, 2011 in the attempt to challenge other social networks and for a time linked other Google products like Blogger and YouTube.

Facebook SDK

   The Facebook SDK for JavaScript provides a rich set of client-side functionality

Twitter API

   You can access Twitter via the web or your mobile device. To share information on Twitter as widely as possible

Apache

   The Apache HTTP Server, colloquially called Apache, is free and open-source cross-platform web server software, released under the terms of Apache License 2.0. Apache is developed and maintained by an open community of developers under the auspices of the Apache Software Foundation.