QUOTE:
Can you explain the term stop of light and it's importance?
a stop of light geez ummm errr try google

google is everyones friend!
each aperture has a number eg f8 or f4 or f2.8
there is a scale going from say f2.8 to f32 each single change is one stop, but be careful as some lenses/cameras allow half or third of a stop changes in aperture
aperture along with film speed (ISO) directly affect shutter speed, the faster the shutter speed the more likely you are to freeze movement (good for jumps, bad for side ons at slow corners)
so getting back to stops:
* if you hear a tog talk about opening up a stop, what they mean is they are letting more light in to the camera (and thus getting a faster shutter) eg going from f4 to f2.8
* if you hear a tog talk about closing down a stop, what they mean is they are letting less light in to the camera (and thus getting a slower shutter) eg going from f2.8 to f4
Your choice of aperture also directly affects "depth of field" (or how much of the photo will be in sharp focus) but thats another story, google "depth of field" if you're interested