it's from Wendler (definitely worth looking up

) first set (after a warmup) is a set of 5 @ 75% of your 1 rep max, set of 3 @ 85% of your 1 rep max and a set of 1+ (meaning as many as you can manage) at 95% of your 1 rep max- as your very close to your 1 rep max- it generally isn't a lot

, the last set is 10 reps @ 70% of your 1 rep max
Wendler is often called 5/3/1, but that's deceiving as that is only week of a 4 week program, the first week is 5/5/5+ (@65/75/85% of 1RM), the second week is 3/3/3+/10 @70/80/90/70% of 1RM (again the + means as many reps as possible for that set), the 3rd week is in the above paragraph, week four is a light week (5/5/5)
after completing the four weeks (squats, bench, deadlifts, overhead press) you add 10 lbs to your squats and deadlift and 5 lbs to your bench and overhead press and repeat the four week program and keep repeating as long you as complete the required reps
his strict program calls for lifting each of those lifts on separate days, I do too much running/hiking to make that happen so combine squats/bench on one day and deadlifts/overhead press on the other- thus far it's worked pretty darn well
