OK.. so I thought about describing exactly what a headset was in my last post.. but i am lazy. I will now clarify.
ALSO… Here is a nerdy picture from that time I rode my bike from Portland to San Francisco.
The red dots are where the headset goes. It allows you to turn your front wheel. And if you have a Chris King headset, it will turn like buttah.
Just to give a perspective (money-wise) I spent 270 dollars on the frame (in the photo above, the frame is the purple part.. but not the bags on the back) that I am building into a bike, so I just spent half of that on the part that makes it turn. I am officially a bike nerd.