Image is thousand times more illustrative then words, so here we have some videos which may explain you the Sitecore.
Rated as a “Positive Product” by Gartner Research, Sitecore has emerged as a leader of the pack among .NET CMS Products. Sitecore makes it effortless to create content and experience-rich websites thus helping you achieve your business goals such as increasing sales and search engine visibility, while being simple to integrate and administer. Sitecore lets you deliver sites that are highly scalable, robust and secure. It automates your processes, and lets you deliver results faster. Sitecore CMS brings flexibility, scalability and ease of use to your Marketing, IT & other business users. Sitecore - A True Web Content Management System
Ease of use:Sitecore is intuitive and easy to use Web Content Management system for business users with what-you-see-is-what-you-get template builders. It is like using Microsoft Word 2010!
Rich Features:A rich feature set with ready to go out-of-the box customizable modules such as blogging, SEO and RSS along with built-in, strong localization support for hundreds of languages.
Alignment with Microsoft Technologies:Sitecore is a pure .NET system ideal for Microsoft environments & offers ready integration with Microsoft products such as SharePoint, BizTalk and Dynamics.
Flexible Workflow & Architecture:Sitecore provides flexible workflow capabilities that allow you to manage the content publication process the way you want. It is also easy to integrate with other technologies and its extensible APIs allow deep customization.
Online Marketing Suite (OMS):Sitecoreâ€™s OMS is enjoying widespread market acceptance today for its incredible features including Real time personalization, Visitor experience analytics, Sales team enablement with web prospects and many more..