And just to confuse the issue further those abbreviations represent combined words such as:
Sd Kfz = Sonderkraftfahrzeug = Special purpose vehicle
Pz Kpfw = Panzerkampfwagen = Armoured fighting vehicle = Tank
For example the PzKpfw IV (short barelled version) was referred to as:
Panzerkampfwagen IV Ausf F (Sd Kfz 161). Improved or modified versions of 'special purpose vehicles' (which covered numerous weapon types) gained additional number(s) for example the long barelled Mark IV (Ausf2) was called Sd Kfz 161/1
Btw Ausf is German for Model/Mark/Design for those that don't know.