My friend explained it to me this way- Say you have a line of 22 people. If you just want the first three people in focus, set your camera at f/3. If you want to have the first 8 people in focus and the rest blurred, set your camera at f/8. And if you want to clearly show all 22 people, set your camera at f/22.
I can't wait to play with the aperture some more this weekend. So, who's following along with me? Have you had a chance to read through the first week?