Straight from texas dps site
http://www.txdps.state.tx.us/DriverLicense/dlClasses.htm
Classes of Driver Licenses
The class of a Texas driver license is determined by the:
Type of vehicle operated on a Texas roadway
Gross vehicle weight rating (GVWR) of the vehicle or the gross combination weight rating (GCWR) of the vehicles towed
Number of passengers the vehicle can hold
Unless prohibited by the Commercial Driver License Act, the holder of a valid driver license may drive all vehicles in the class for which that license is issued and all lesser classes except motorcycles and mopeds.
Classified Driver License
Class A, B, C, and M driver licenses are issued to individuals who are exempt from obtaining a commercial driver license (CDL) or who are not required to obtain a CDL.
NOTE: Individuals who are exempt from obtaining a CDL may still be required to obtain a Class A or Class B driver license if the type of vehicle driven meets the definition of a commercial motor vehicle.
Individuals who are exempt from obtaining a CDL but may need a Class A or Class B driver license are:
Operators of recreational vehicles driven for personal use
Some farmers who meet certain criteria
Operators of cotton-seed modules or cotton burrs
A fire-fighting or emergency vehicle operator
Military vehicle operators
Vehicles owned, leased or controlled by an air carrier
For more information on exemptions, please refer to the Texas Commercial Motor Vehicle Drivers Handbook.
Classification
Description
Class A
Authorizes an individual to drive a vehicle or combination of vehicles:
Not described under a Class B or Class C driver license
With a GVWR of 26,001 pounds or more provided the GVWR of the vehicle(s) towed is in excess of 10,000 pounds including vehicles in Class B or Class C
Class B
Authorizes an individual to drive:
Any single vehicle with a GVWR of 26,001 pounds or more and any such vehicle towing a vehicle with a GVWR that does not exceed 10,000 pounds or a farm trailer with a GVWR that does not exceed 20,000 pounds
A bus with a seating capacity of 24 passengers or more including the driver
Any vehicle included in Class C
Class C
Authorizes an individual to drive any single vehicle:
Or combination of vehicles that are not included in Class A or Class B
With a GVWR of less than 26,001 pounds towing a farm trailer with a GVWR that does not exceed 20,000 pounds
Designed to transport 23 or less passengers including the driver; vehicles rated as 16-23 passengers including the driver require a Class C CDL unless exempt
Class M
Authorizes an individual to drive a motorcycle or moped.
Class of Commercial Driver License (CDL)
Individuals who hold a valid CDL may drive all vehicles in the class for which that license is issued, including their personal vehicle (but not a motorcycle or moped).
Classification
Description
Class A CDL
Authorizes an individual to drive any combination of vehicles with a GCWR of 26,001 pounds or more if the GVWR of the vehicle(s) towed exceeds 10,000 pounds.
Class B CDL
Authorizes an individual to drive any:
Single vehicle with a GVWR of 26,001 pounds or more; any one of those vehicles that is towing a vehicle does not exceed a GVWR of 10,000 pounds
Vehicle designed to transport 24 passengers or more including the driver
Class C CDL
Authorizes an individual to drive any single vehicle or combination of vehicles that is not a Class A or Class B if the vehicle is:
Designed to transport 16 to 23 passengers including the driver
Used in the transportation of hazardous materials that require the vehicle to be placarded