What do you call the cars used inside airports?

Golf carts are frequently used both inside airport terminals and on the apron to transport passengers, crew, and small amounts of luggage. These are usually referred to as "golf carts" but may also be called "courtesy transports" on an official level.

The small tractor-like vehicles you see pushing & pulling aircraft, baggage carts, and assorted other equipment are called "tugs."

Large airline-type aircraft are usually pushed or pulled by a large truck called a "pushback truck" but these can be referred to as tugs as well.