Sitecore and EpiServer are WCMS with an enormous presence on the web. Both use .NET technology which only works on IIS and Windows based. Both have a great developer community on their developer sites. The main storage system is MSSQL but Sitecore also uses Mongo to manage analytics information. This content management systems are used to create complex websites because of their facility to build and manage new content.

An introduction to Sitecore Speak featuring a basic example application.

Sitecore is a Customer Experience Management company that provides web content management and multichannel marketing automation software. WordPress, on the other hand, is a Content Management System that can be used to develop any website, simple or complex.