The main components of the system are the fighting styles. Each fighting style consists of two parts, each of which requires one feat. Style Basis gives some minor static ability, or a modifier to your basic attacks, and Style Expertise gives you a few tricks you can pull off if you battle surge (which you can only do a few times per combat) or have combat focus (which requires a standard action to achieve, but remains until you expend it to perform some sort of immediate interrupt).
For instance, the Two Weapon Fighter style lets you, instead of attacking with one weapon as a standard action, spend a standard and minor to make two attacks against the same target. That's the basic ability. If you spend a second feat to get the expertise, then a few times per combat you can battle surge to make two attacks (at the same or different targets) as one standard action, and if you have your combat focus you can expend it to reload two weapons at once, even if you have no free hands.