These days, the ladder truck usually has a very big ladder on the back and some smaller ladders. Usually a pumper has to pump water to the ladder truck. Tankers carry water - and lots of it. Tankers are useful when there's a fire someplace where there's not a fire hydrant nearby. Usually the tanker sends water to the pumper through a big hose.
Tankers can also drop off their water in a dump tank, which is like an above-ground swimming pool.
The pumper then sucks the water out of the dump tank through a hose. Rescue trucks sometimes look like ambulances, and sometimes they're much bigger. The rescue truck carries medical supplies and tools for helping people who have been hurt at a fire or in an accident. A rescue truck carries specially trained people called Emergency Medical Technicians or Paramedics. Often they are also firefighters.