Let's start from the beginning:
If I said you should do 3 exercises - 4 sets - 10 reps for your biceps, it would breakdown like this:
Bicep Workout
==========
Exercise 1. Dumbbell curls (single arm) - You would do 10 reps on your left arm, then 10 reps on your right arm. Next you would rest for 60-90 seconds before starting again. The 20 total (10 reps for each side) constitutes a set. So, you would repeat this exercise 3 more time to have a total of 4 sets of this particular exercise.
Exercise 2. Curl bar curls - You would do 10 reps of curls using an ez-curl bar. Next you would rest for 60-90 seconds before starting again. The 10 reps constitutes a set. So, you would repeat this exercise 3 more time to have a total of 4 sets of this particular exercise.
Exercise 3. Straight bar preacher curls - You would do 10 reps. Next you would rest for 60-90 seconds before starting again. The 10 total reps constitutes a set. So, you would repeat this exercise 3 more time to have a total of 4 sets of this particular exercise.
Make sense?
-Rip