The understanding I got from aperture was that it is the area that controls where the light comes from. From the concept shutter speed I leaned that it controls the duration of the exposure. In ISO speed it is where it controls the sensitivity of the camera’s sensor to a given amount of light, it is also preferred to use a lower ISO speed. The camera modes are auto, program, aperture priority, shutter priority, manual and bulb mode. Each of these shows how each mode is used for a given exposure. Exposure mode also has portrait, landscape, sports/action, and night/low-light.