Matt, EMM is a separate ticketed event available to anyone who wants to pay. It's limited to I think 500 people and allows access to 7DMT, PP and Pooh before anyone else is in the park. There's also a breakfast buffet available until 10 AM. My kids got 11 rides in during that hour and were able to walk onto Space Mountain because they had a head start on the rope drop crowd.
EMH is Extra Magic Hours, available exclusively to resort guests. Most of the park is open, but it's often crowded because there are 30,000 hotel rooms at WDW. But it is included as part of your resort cost.