PX4 - and PRM-03

Hi guys!! I am creating a drone as an undergrad. I have been searching PX4 pinouts everywhere and cannot find a good one.

Is the PX4 compatible with the PRM-03?

All of the pin outs i see for pixhawks include it! Is it needed for the PX4?

Thanks!

What PX4? Which hardware is that? Do you have a picture?