It is one stage that its score gives you your classification. The classes go Unclassified, D, C, B, A, Master, Grand Master. It is the average of the last four classifiers that gives you your rateing. When you shoot USPSA the scoring is that you can win your class among other shooters of the same ability.
In USPSA it's usualy called a "Classifier" stage. It's a stage taken from the
book of classifiers. Set up and run the same no matter where you shoot it.
The purpose is to determine your skill level and assign a "classification"
(D, C, B, A, Master or Grand Master) within a Division. What division
are you shooting in?
You will get an initial classification after shooting 4 classifiers in any
division. After that your classification is based on the average of the
best 6 of the previous 8 classifiers within that division. Sounds more
complicated than it is. Pretty good explanation in the rulebook. You
should have gotten a copy when you joined USPSA.