What does the headset in a SLR camera mean?

The main part of an SLR is the body and lens. In order to promote sales, manufacturers sell the body and lens as a set. Such lenses are called kits. It is just one less package than the independent lens. We can see it on the outer packaging of the camera. Like Rabbit, they will mark only the body, which is a stand-alone 5D MarkII. If they mark a kit, it will be a 5D MarkII body plus a 24-105 lens. This 24-105 lens is called a kit lens. Buying a set of machines is more cost-effective than buying them separately, but you should make your choice based on your own needs.