In common fitness parlance, 'reps' means an individual repetition of an exercise, according to Crossfit NYC. Whenever someone says, "You need to do X reps in this set," the person means the exercise needs to be done X number of times before moving to the next exercise.
Common knowledge holds that an ideal rep range for most beginner strength training workouts is from 8 to 12 reps. If someone can do more than 12 reps, there isn't enough resistance. On the other hand, if it is too difficult to do 8 reps, the weight is too heavy for consistent gain.