A CDL is a commercial driver's license, according to the U.S. Department of Transportation. Operating commercial motor vehicles takes more know-how and skill than driving regular vehicles, thus the need for a separate license. Drivers get their CDLs from their states and can be licensed in only one state.
To get a CDL, a driver should read his state's commercial driver's licensing manual and determine the CDL class and special endorsements he wants, such as for driving a school bus, according to the DOT. The next step is a permit that allows a trainee to drive with a person who has a CDL. The final step is to pass CDL testing and submit the proper documentation.