A commercial driver's license (CDL) is a special license required to operate large or heavy vehicles, such as trucks and buses. It ensures that drivers have the necessary skills and knowledge to safely handle these vehicles on public roads. There are different classes of CDLs, each allowing the operation of specific types of vehicles. To obtain a CDL, drivers must pass both written and driving tests that cover topics like vehicle operation, safety regulations, and road signs. Additionally, some drivers may need to obtain endorsements for specialized vehicles, such as tanker trucks or passenger buses.