A tower is generally built to take advantage of their height. Towers are usually taller than they are wide. They can stand-alone on the ground, or they can be part of a larger structure or device. Generally a staircase tower or an observation tower is built with brick or stone. Sometimes a masonry tower is a separate structure on the grounds designed to be a water tank or silo.
A turret is a small tower that projects vertically from the wall or from the edge of a building, but does not continue to the ground. Originally, turrets had a military use and projected from a medieval castle to provide a defensive position. Later they were used for decorative purposes. They can have a circular top with crenellations or a pointed roof.