Each game of Zero-K you play now shows on user's page .. you can also easilly replay demo of it:
http://zero-k.info/Battles.mvc/Detail/2191
Players are awarded XP from battles. XP depends on victory/defeat, probability of victory (unlikely win = more XP), game size (smaller = more XP), bots and other factors.
XP is used to level up and each level up you can spend your XP to buy various components.
Chassis, modules and weapons for your commanders

Using purchased components, you can customize up to 4 different commander setups.
This is example of one of mine:

At the start of game, you pick which of your commanders you want to use that game.
Each commander starts game at level 1 morph and can gradually morph up to level 4, gaining HP, strength and activating more and more modules.
If you can model, please help us making proper awesome commander models

Ideally commanders should become more and more awesome as they morph and display various modules graphically.
To try this, simply play few zero-k games and then login to http://zero-k.info/ to unlock stuff and customize commanders.