if you get a CLD C, you can get a hazmat endorsement, or a Passenger endorsement. So you can drive a commercial vehicle <26,000 LBs that may require one of those endorsements.
lf you get a CDL B, you can drive a straight truck, and can get several different endorsements, which allows you to drive specific vehicles or types of cargo.
lf you get a CDL A - you can drive a semi-truck, and additionally get various endorsements, that will allow you to drive any type of commercial truck/bus
Or you can drive a Cab; see posts 2,3,4.