The acronym of EMD is Exact match Domain. This had launched by Google in 2012 to stop ranking exact domain names for a short and long tail keywords on SERP.Why it is Launched?
Previous SEO people has find a strategy to get easy ranking on Google SERP (Search Engines Results page). For that they are choosing the domain names as stuffed with service or brand oriented keywords. As Google gives importance to domains which has more relevance sites, their sites gets ranked when searched for their service or brand names.
As a result,many people had followed this type of strategy and purchase their domain with keywords. For a couple of years this has bought a good business for them. But when you searched with their related service keywords, low quality sites are getting easily ranked while high and authority sites gets less ranked.
To overcome this situation, Google has developed an algorithm to eradicate such low quality sites. So at this EMD Update has been released in September 2012. So official domain gets less ranked on SERP. At this case, we can say this is a blunder i.e, (also an update) launched by Google in September 2012 to prevent poor quality sites from ranking well simply because they had words that match search terms in their domain names. When a fresh EMD Update happens, sites that have improved their content may regain good rankings.
Examples for Exact Domain Names, if you searches as word in brackets
(Forum for cupcakes) "cupcake-forum.com"
(Web Design Company) "webdesigncompany.com"
(Seo Company Hyderabad) "seocompanieshyderabad.in"
Before EMD, like these many sites are ranked on 1st page, after launching many of these sites are not even ranked with in 100. So we can say these sites are not having authority or back links compared to their competitor sites.