no problem: here's a couple images of what it is. Click me
It's simply a mechanism to help regulate air flow into the intake manifold. The more you press down on the accelerator, the more the plate rotates to open to allow more air in, which the car computer should compensate and add more fuel to the mixture when dumping the mixture into your cylinders. The throttle body is somewhat warmed up by your coolant and thus you also have coolant passages in it to keep the body warm so your air entering the intake manifold is somewhat related to engine operating temperatures, especially inportant during warm-up sessions. There is also a good amount of people that believe the coolant bypasses in the TB affect performance after warmup as now you are running hotter air which is less dense and thus for summer months, they disconnect all coolant passages to the TB and route the inlet and outlet together. I know completely useless for this thread but thought I'd through that in. Anyway, so why does it get dirty if only air is entering this body, you might be wondering? It has to do with blowby gases that come about from your PCV (positive crankcase valve), what happens is excess gases buildup in your engine area and to relief them, they are routed through a line back into your plenum. That's the main culprit, other issues arise from an airfilter that has holes and allow particles and dirt particles to enter the intake plenum.

To find it, it's where your cable ends that starts from the accelerator pedal. Another way is to follow your air filter box, follow the black plastic hosing line (called your plenum) to a metallic body that you will see the cable sort of wound half way around this linkage. That is your throttle body.