Raising the ISO will allow you to shoot at a higher shutter speed. Professional sports photographers use a shutter speed of around 1/1000 of a second to stop motion. During the day this is simple. At night however, you may need a faster F Stop than your lens is suited for. To compromise, you increase the ISO (what used to be film speed) of your camera. This now allows your camera to see more light. Shoot from different angles and capture your surroundings.