Rm stands for Rep Max. so the phrase 1RM essentially means what weight can you lift a maximum of 1 time. If my maximum squat is 300 pounds, i.e. this is the absolute maximum weight I can lift just once, then my 1RM is 300. If I can lift 280 twice, then my 2Rm is 280 and so on.

A rep is short for repitition and basically means 1 lift or 1 jump. me say to you give me 10 reps of tuck jumps is just another way of saying please do 10 tuck jumps.

I hope all that makes sense.

Cheers

Jaydub