There are a great many different types of fire trucks.  All have a different job to do.  Some pump water, some raise ladders, and some are used to take people to the hospital.  Many are used to carry the equipment firefighters need for a special emergency, like a train wreck or a building collapse.

A truck that pumps water to the fire is called a "fire engine" or a "pumper".  Today, most fire engines also carry hose in a large storage area in the rear of the truck.

The term "fire truck" usually means any other type of truck used to carry equipment or people to a fire or emergency.  When a firefighter says "truck" though, he usually means a "hook and ladder" or "aerial ladder" truck.  This type of fire truck carries a large assortment of hand ladders and has a long extending ladder that can reach as high as 120 feet or about 10 stories high.