To operate a commercial motor vehicle, such as a semi-truck, you must have a commercial driver's license (CDL). A CDL permit allows you to practice driving a commercial vehicle with a licensed CDL holder as your instructor, but it does not allow you to drive a commercial vehicle on your own.
To obtain a CDL, you must pass a series of tests, including a written knowledge test, a skills test, and a vision test. You must also meet certain medical and physical requirements.