What's a class 3?

Today I will have to agree with Kelsey and say that it wasnt the bestest of days. I had a very sweet lady as my patient and she was totally needing a more experienced hygienist. She ended up being a class three and i was messing up left and right on EVERYTHING! I apparently dont know how to probe a mouth that isnt a 1B. But, i survived and so did she :) Although, i feel soooooooooo not ready to see pts especially when they are class 3!