What is webcenter?

I tried to understand what is the use of this tool but could not understand much from blogs and oracle docs.

My questions are:

1. What are the highlights/features of this tool which make any company or architect decide that this is the appropriate tool they need for their web application?
2. How is different from other java IDEs like netbeans and eclipse?

WebCenter is not a tool. It is a branding of 3 different technologies brought together to support user interaction via web sites (WebCenter Sites = Fatwire), portlets, content management (WebCenter Content = Stellent), and WebCenter Portal, rebranded from Spaces (which is similar to MS Sharepoint) is a pre-built web site with support for collaboration and integrates with Sites and Content. We use Jdeveloper to design and build the pages (ADF Faces - JSF) that make up the sites, we use the Sites tool to build the site and WC Content has it's own interface to check in content, edit, manage, search, etc. Lots here and here as well as: WCContent, Sites, Portals. You might also want to download the free Virtual Box image here, and play with the software. There are myriad books and tutorials that can be found with a little searching. Also, consider taking a class with Oracle which will explain these technologies in detail. Also, my aggregation site here, lists many books, blogs and tips that may help.