Two terms I don't understand - please explain

Slam = dynamic impact, i.e., how well loud, fast extreme transients are rendered.

Prat (or PRaT) = Pace, Rhythm and Timing -- a component with PRaT gets your toes tapping, let's you hear an feel the drive and pulse of a tune (maybe even puts it there, in some cases, e.g., where a TT spins too fast). Pretty much the same thing as boogie factor.

Roughly, anyway.

Jan, most often slam refers to bass impact. That is you feel the sound waves hitting you rather than just hear the notes being played.

PRAT refers to Pace Rhythm And Timing. This applies to all playback media not just analogue . If a system has poor PRAT it appears slow and lifeless. Good PRAT means that it is alive much as the real event would be.

I will leave to others with more knowledge than I have to explain why we perceive something as having good PRAT.

Phaser's explanation of slam is better than mine. It refers specifically to bass transients.