In the singleplayer game you are the GDI command 'Havoc.' In the missions outside (in the open air), sometimes NOD soldiers are dropped out the air. That is very cool. You have very much live in this modus, and can upgrade your healt maximum too. The NOD soldiers are dead, just as you shoot them. But that is not bad, because there are many soldiers.
Your rival is the NOD commando 'Sakura.' You can see her sometimes in the game.
I think this is all I can say, you will just have to test it yourself!