I find that sometimes I think I understand something well but because I don't have to apply that understanding (or lack thereof) I can get along fine without learning that oops - I had it wrong.
In the first class, we covered the differences between cassettes and freewheels (part of the rear wheel) among other things. Of course, I could have simply looked up the subject on Sheldon Brown's site but I double that I would have as good an understanding as I do now, having been walked through the exercise with real parts by a real person.
