Some systems are just CAD. Some are just CAM. Then some are both CAD and CAM. What I do personally is use Dolphin cad cam for my drawings and machine. The best and simplest way to describe it is, design you're part in the cad. Once you have done so, you pass it over to the CAM side to set up you're machining operations. Simulate it and make sure everything looks ok. Then select you're post processor, I personally use mach 3. You will need some sort of controller software. Mach 3 is pretty cheap and nice.