How different is this cheese from Parmigiano Reggiano?
excuse spelling please, it is all a cut and paste to ask this question.
I've been googling to answer my question.

I'm making Potatoes au Gratin and wanted Parmigiano Reggiano but my
block is so hard that I didn't want to spend time grating it so picked
up an already grated container from the deli but it wasn't Parmigiano
Reggiano when I got home, it was Pecorino Romano. How different is this?