The Zone of Proximal development to me is the gap between what a child knows and what he or she may not know. The difficult part of this to understand is how to continue that knowledge better. The child learns from the teacher and models them until he or she can do them on their own without assistance.
I think that this is vital in understanding when you are a teacher because it could help us in having the student become the best learner that they can be. One example that I can think is that I was a soccer coach for a time to nine and ten year old boys. At first they did not want to take me seriously because I was a girl, but I scaffold first their idea that a woman can play soccer, but that I showed them things that they could not do yet, such as juggling. After showing them repeatedly over a couple weeks of practice, the boys did not need me to model how to lift the ball anymore, they could do it themselves. Some still looked at me for guidance, but when I said start juggling they did not need me to model for them.
Looking at my own learning, I can see where my teachers had applied this method. Mr. Hansel my fourth grade teacher was teaching us how to find the area of a triangle. I remember area very vividly for some reason and I remember that we caught on to the triangle pretty easily. However, he started to mix area with fractions, and that took many days for me to be able to apply the concepts I learned when using whole numbers to fractions. I remembered Mr. Hansel had to constantly help me through by showing me models or prodding my thinking along by asking questions.
My biggest concern is that of almost every subject so far, how to apply it to a classroom of twenty six students. Not everyone is going to be at the same level, and while I can see how some of my elementary teachers did achieve that, I always doubt if I will be able to. I think that ZPD is something that is important to a classroom, but one of the hardest to think about on a individual basis and thinking of it on its own.