As a general rule, the bigger the diameter of the lens, the more light that is available to make the photograph and, as a result, the better the photo quality. The farther away the lens is from the back of the camera the bigger the lens needs to be. For this reason, tiny point and shoot cameras are thin with small lenses and SLR's are thick with big lenses. (SLR stands for single lens reflex, or cameras that show in the viewfinder the exact scene that the lens sees.)
In conclusion to Part 1, manipulating ISO, Shutter Speed & F-stop allow you to create different effects of the same image that you are looking at. If you want to freeze action, for example, then use a higher ISO and a faster shutter speed (a shutter speed of 1/1000th of a second will freeze most action). If you want to take a panning shot with a kid on a speeding bicycle going past you, for example, (panning is when you swing the camera and track the object you are photographing), and as a result, streak the background but keep the object sharp, then you will want to use a slower shutter speed and a lower ISO. For pan shots, 1/15th of a second up to 1/60th usually work well, depending on how fast the object is moving. When you pan, just try to keep the part of the image you want in focus in the same place in the viewfinder as you snap the photo.