What does RPM mean in a propellor aircraft, compared to a jet aircraft? What is the practical significance of speed RPM in a propeller aircraft for a pilot? I am not able to correlate it with RPM in jet engines?
RPM in a propeller aircraft is typically under 2400, as the prop spins at the engine RPM speed. Above 2700 the tips of the propeller begin going supersonic and make more noise than anything.

Jets engine spin much faster, as discussed here
Which are typical rpm values for aeronautical turbines?