The Firebase, from the sound of things, is a portable UNSC base of operations and presumably the first structure players will start with. It is capable of constructing vehicles and deploying troops. The base also features a 'lock down mode' which you can see on the left of the image above.
The Warthog sounds as you would expect, though a few new details are revealed. For one, Warthogs are available in three flavors: unarmed, chaingun, and gauss cannon. The unarmed variant is the most basic unit, whereas it sounds like the others will have to be acquired via upgrades performed at the Firebase. Good stuff. Here's hoping we'll get new information on a more regular basis from now on. Hit the source link for more images and even a short Flash video of the Firebase in action.