The 10RM (Ten Rep Max or Ten Repetition Maximum) is the weight you can lift for exactly 10 reps on a given exercise. For example, if you did a set of 200 lbs for 8 reps, you can use a 10RM calculator to work out that your 10RM was 186 lbs. That means you could have done 186 lbs for 10 reps.
Since your 10RM strength is based around sets with 10 reps, you can compare this with sets that use a different number of reps. For example, if you do a set with 215 lbs for 8 reps and another with 185 lbs for 12 reps, the 10RM is 200 lbs in both cases. This way, you can immediately see that your performance was the same in both sets.
Also, the 10RM can be used to evaluate your progress very well: If the 10RM increases (in the long term), you will become stronger—no matter what the weight and reps look like.
To find out what your 10RM is for a particular exercise, check out our Rep Max calculator.
Since this is a lot of math to do while you're training, the Alpha Progression app will automatically calculate the 10RM for each set. You can also see the progression of the 10RM of an exercise over time in the graphs on the app. You can immediately see from the graph if you are progressing.
In addition to the 10RM, there is the 1RM, which follows the same principle but, as the name implies, calculates how much weight you can move for 1 rep.
An often-used alternative to the 10RM is training volume. However, this is inferior because it "rewards" high reps far too much. By only considering the training volume, you could experience a "fake progression" by doing more reps and using far less weight.