GPF and OPF refer to particulate filters used on modern petrol engines.
They perform a role similar in concept to a DPF, but the systems are not identical.
They are particularly common on modern direct-injection petrol engines.
A simple way to remember the difference is:
DPF = Diesel Particulate Filter
GPF / OPF = Gasoline / Otto Particulate Filter
The control strategies and regeneration behavior can differ significantly between them.