EMD (Exact Match Domain) is a filter Google launched in September 2012. its importance of keyword oriented domains and quality sites from ranking

The EMD Update for Exact Match Domain is a filter Google launched in September 2012 to prevent poor quality sites from ranking well simply because they had words that match search terms in their domain names.

EMD means Exact match Domain. And if you want to know more about Google EMD update then read this articles carfully: http://searchengineland.com/library/google/emd-update