As most trainees know there are different ways on how to prescribe or measure the weight on a bar. This is a small glossary of terms one encounters frequently, as it probably be also can be found elsewhere on the web, but well, now I have a link handy.

Load, weight on the bar, absolute load

Just the absolute weight on the bar (bar included). 200kg is 200kg, 100kg is 100kg. Apart from competitions, it is a useful tool to assess your overall progress. If you could bench 80kg five times at one time and two years later you can bench 100kg five times, you probably not only got better at benching, but also built up your benchin' muscles.

1RM, nRM, one rep max, n rep max

The 1RM or in long form, your one repetition maximum, is the maximal amount of weight you can lift for one time in a given exercise. Analogously there are nRM for any n you can think of, describing the maximal amount of weight you can lift for n repetitions. In terms of muscle accretion, 1RM does not seem to be very indicative, but if your 5RM or 10RM in a given exercise (without big form change) goes up significantly, it usually indicates that you have built some muscle somewhere.

Intensity, absolute intensity

The intensity is the relation of the load to your 1RM and expressed in percentage. If your 1RM in the bench is 100kg and you have 80kg on the bar, it is an 80% intensity. It is not a description or perception of effort, even though lesser educated folks or people foreign to the sport might use in that way, but that's just like non-technical people mistaking the monitor with the computer back when desktops were commonplace. The term absolute is usually dropped, unless you want to make the distinction clear to the next item on the list, namely

Relative intensity

The relative intensity is the relation of the load for a given number of reps to your repetition maximum for that number. To keep the numbers simple, if your 10RM in the squat was 100kg and you would do sets of 10 with 80kg, it would again be 80% relative intensity, although the absolute intensity would probably be far lower.

RIR, reps in reserve

The number of reps you could still do if you were to push a set to technical or muscular failure. A RIR of 2 would mean that you finish the set at a point were you could still do two more reps. Note that beginners often totally misjudge this number and may call a set RIR 2 if in reality they could still perform ten more reps. Can be used both retrospective to judge how hard a set was or prescriptive so a lifter can autoregulate their training, then accompanied with a rep range, e.g. 10 reps at RIR 1.

RPE, rate of perceived exertion

With RPE you assign a number, commonly in the range from 0 to 10, to the set you just performed, representing the effort you perceive, with 0 being no effort at all and 10 being a maximal effort. Most of the time one designates the RPE with an "@" and this also found its way into spoken language. When first training with RPE it's useful to equate it with RIR as mentioned in my manpage on repranges, but this is only a rough guideline. Near maximal singles can be of a lower RPE than @10, even though there might be no rep in reserve, whereas squats with more than 15 reps are often perceived as @10 no matter how many more reps you can grind out.