Share-Nothing architecture

In this forum, people are talking about share-nothing architecture. I
don't understand what this term means and how this improves the
scalability

"Share Nothing Architecture" is a common pattern for scaling out Web
applications.

Generally speaking, the idea is to remove dependency between the scaling
units, which in the case of a Web application means the Web Servers.
Once these units become independent from each other, you can easily
scale them just by adding more units. You can then load-balance the
incoming requests among the different Web Servers.

http://www.zefhemel.com/archives/2004/09/01/the-share-nothing-architecture
http://www.gigaspacesblog.com/2007/04/06/shared-nothing-architecture-redefined/