So its my understanding that a few years after oblivion titus mede conquered the imperial city and named himself emperor. Over the course of 200 years Elswer becomes independent then Black Marsh follows and invades and conquers Morrrowind. Valenwood and Summerset Isles also leave under the control of the Aldermi Dominion and the Thalmor. Now Skyrim wants to leave the empire and civil war has broken out.

So first off all is this correct.
second anyone no whats happening in hammerfell high rock and cyrodil
third could someone explain what thalmor and aldermi dominion is all about.

The Thalmor are the ultra-radical rulers of the Aldmeri Dominion who were at the head of the Dominion before Tiber Septim conquered them with the Numidium. The Thalmor believe that mankind is bad, as is the world and believe the only way to return to their previous god hood before the creation of Nirn is to destroy it and remove man from the wheel of possibility. Basically, they want to destroy the world so they can go back to being spirits like the Aedra and Daedra. The Aldmeri Dominion is the nation they control, consisting of Summerset Isles and Valenwood.

As for whats going on in the rest of the world, well alot of stuff is still unknown. As of Infernal City, Morrowind was devastated by the Red Year and the Ministry of Truth fell on Vivec while the Argonians controlled by the Hist invaded. The Empire fell and Mede took over, controlling only Cyrodiil as the other proviences broke away. As of Skyrim however, obviously the Mede Empire or some other dynasty has succeed in extending their influence outside of Cyrodiil, but to what extent we won't really know until the game is released.