What's the difference between a skeg and a rudder and why do I need one?

What's the difference between a skeg and a rudder and why do I need one?

A rudder helps you steer your craft with less effort, and, in windy conditions, can be used to avoid weather-cocking by setting it at an angle. While a rudder is useful for kayaks longer than 14 feet, once you gain the ability to edge-turn your kayak, having one becomes less of a concern unless you are under full load camping gear in big water. 

A skeg stores inside the hull of your kayak and can be lowered into the water to improve the straight line tracking in most conditions. It has no ability to control direction/steering. 

Both rudder and skeg can be deployed and retracted while seated in your kayak by using the control system positioned to the right side of the cockpit.

Please see attached images for more info.