A sub-race is chosen by the player when he sets up his homecity (kind of like a character in an MMORPG), after choosing a race. What do you mean 'get'? We listed some of the benefits of the various locations you can choose for your race earlier, but not all of them. And no, I can't say anything more specific about bonuses.
Oh, also, each sub-race has a different location on the world map. I think you could find these yourself by comparing our released world map with the MMORTS showcase location names.