Thickness is a common term used in the blade industry. The thickness of a blade will help to determine the speed and quality of your cut. There are advantages to both thick and thin, if you are going to use them on a regular basis it is to your advantage to know the difference.
Faster precise cuts are created by thinner disks. Thin blades mean that less material is being used against your cutting material, creating a faster rotation of the blade. It can also mean fewer sparks/dust are created and that your blade will not heat up as fast. This allows the operator to cut for longer periods of time.
Thicker disks are typically cheaper, slower, and have increased control. Thicker disks are used in areas like concrete widening. They will burn incredibly warm and require more cooling time before dismantling for the day.