Boxing coaches call punches by number so a whole class can follow one call: 1 jab, 2 cross, 3 lead hook, 4 rear hook, 5 lead uppercut, 6 rear uppercut (sample note).
Odd numbers are thrown with your lead hand and even numbers with your rear hand. If you box southpaw, the numbers stay the same and the hands swap.
Defence is called by name: slip, roll, block. A call of 1-2-slip means jab, cross, then move your head off the line.