PWM fans control their speeds automatically. You can control any fans that are connected to the motherboard through software.
A fan has to be PWM (4-pin connector, not 3-pin) and plugged into a PWM fan header (4-pin) for it to work as a PWM fan.
Ah ok, thanks for that. So as long as the fan has a 4-pin connector it will be PWM? I'm guessing all case fans are 4-pin then?