Push Pull solenoids consist of a solenoid coil with an armature—a metal plunger—in the middle. When the solenoid coil is energized, the plunger is pulled into the center of the coil. This makes the solenoid able to pull (from one end) or push (from the other)
This push pull solenoid in particular is nice and strong, with a 52 mm long body and a 'captive' armature with a return spring. This means that the solenoid moves when activated with up to 24VDC, and when the voltage is removed, it returns to its original position, which is very useful. Many lower cost solenoids are only push type or only pull type and may not have a captive armature (it'll fall out!) or don't have a return spring. This solenoid has 4xM3 (metric) threaded holes in the side of the housing for easy mounting and assembling.