Well, CDL stands for Commercial Driver's License.
There are three types of CDL: CDL class A, CDL class B, CDL class C
The Class A allows the driver to operate a combination of vehicle with a weight of at least 26,000 pounds. The GVWR of the towed equipment is at least 10,000 pounds. Also you can operate school bus and passenger bus if you obtains the neccessary endorsement.
Some of the combinations may be:
The Class B allows the driver to operate a combination of vehicle with a GVWR bigger than 26,000 pounds. The GVWR of the towed equipment or vehicle is under 10,000 pounds. The last two equipment listed you will need the proper endorsement to operate them. The following equipment are within this classification. Some of them, you will need the proper endoresement.
The Class C is the lower grade of difficulty class. This class alows the driver to operate vehicles with a GVWR of less than 26,000 pounds. The equipment towed for this case has a GVWR less than 10,000 pounds. Also, you can use this class to operate a passenger bus of 16 or more person including the driver. Another particular use is the trasportation of Hazadous Materials (Hazmat)
It is important to know that to transport Hazmat you will need the proper endorsement.