A set of definitions exists in the Senate ESEA bill written and voted out of the HELP Committee (Health, Education, Labor and Pensions).
Reps and sets are terms used by exercise professionals, athletes and individuals in the gym. They provide structure and organization to your workout. If you work with a personal trainer or physical therapist, she will prescribe an exercise based on a specific number of sets and reps.
Reps is the number of times you lift the weight in a row, and sets is the number of times you do that. A safe bet for you would be to do 3 sets of 8-12 reps, with a minute and a half rest in between sets. As a girl, you don't have to worry about building prominent muscle. Most women have to work their butts off and/or take supplements to do that.