Solenoids are basically electromagnets. They are made of a coil of copper wire with an armature (a slug of metal) in the middle. When the coil is energized, the slug is pulled into the center of the coil. This makes the solenoid able to pull (from one end) or push (from the other).
vending machines, game machine, all kinds of automatic locks, security device, IC and coin operated call, etc.