Here are some great resources to learn more about batteries:
General Info on "Pz" batteries:
(O)PzS (Flooded) and (O)PzV (Gel) are both tubular lead acid batteries. They have a higher lead content and more surface are providing them a higher energy density and longer lifespan.
(O)PzS batteries are a form factor designed for traction systems, meant to be put in a pack and bolted together by their terminals. There are 3 main types, PzS, PzB and PzV.
PzS is the Standard DIN style form factor Lead-Acid battery.
PzB is the less common BS (British Standard) form factor Lead-Acid battery.
PzV is either Standard DIN or BS, but in a Gel-Cell chemistry.
PzS means Pz = PanZerplatte (tubular plate) S = Flüssig (flooded) "MOTIVE"
OPzS means O = Ortsfest (STATIONARY) Pz = PanZerplatte (tubular plate) S = Flüssig (flooded)
OPzS are recommended for backup applications (UPS/telecom)/stationary and deep cycle applications, where the battery is actually spending the most part of its life in float operation. That means the electrolyte concentration will stay high for a very long time hence there is an increased chance of plate corrosion (that's why most Battery manufacturers will choose a lower (1.24) electrolyte density).
"OPzS vs PzS" ...
Same electrical characteristics
More electrolyte in OPzS (stationary)
PzS (motive) is designed "stronger" to handle the forces of motion
PzS are cheaper (mass production).