Back in the days of film, I remember taking photos of statues, mostly because it seemed “important” to do.
There are three ways to control the amount of light recorded by your camera. By adjusting each of these three variables, your camera can make sure that every picture you take produces an image with the proper amount of light.
When you shoot in Aperture Priority mode you set your aperture and your camera sets your aperture.
In Program mode your camera will set the aperture and shutter speed. You control your ISO, exposure compensation and other settings.
Composition is the placement or arrangement of visual elements in a photograph. The rule of thirds can also be used to help you position the horizon.