Front Mech

Bottom Pull - Commonly used on road and touring bikes, this type of derailleur is actuated by a cable pulling downwards.
Top Pull - This type is more commonly seen on mountain bikes. The derailleur is actuated by a cable pulling upwards, which is usually routed along the frame's top tube, using cable stops and a short length of housing to change the cable's direction.
Bottom Swing - The derailleur cage is mounted to the bottom of the four-bar linkage that carries it. This is the most common type of derailleur.
Top Swing - The derailleur cage is mounted to the top of the four-bar linkage that carries it.