Aperture is a part of photography that many amateurs lack understanding of. It is a simple concept, though, and one that is important if you want to grow in your photography.
A simple way to better understand aperture is by thinking of it as your eye pupil. As more light comes in, the wider your pupil becomes. And exposure is produced by the combination of ISO, shutter speed, and aperture settings. As the size of the aperture diameter change, less or more light is allowed into the sensor. The aperture should be determined based upon the situation you are photographing. In general, though, the wider the aperture, the more light while the narrower the aperture, the less light allowed into the sensor.
Many beginning photographers are confused by aperture. Part of this is because of the language surrounding aperture. Some will refer to aperture as wide or narrow, while others refer to it as small or large. It can refer to either considering a wide aperture is referring to the opening of the lens being wide, while a large aperture is referring to the f-stop.
The size of the aperture is measured using the f-stop scale. The f-number refers to how wide the aperture is open. The size of that opening will affect the depth of field and the exposure in the final product. It is important to remember that the lower the f-stop, the wider the aperture is open. If the aperture settings on your camera are set to a small f-stop number, your aperture is wide open. When you have a higher f-stop, your aperture is narrow.
The f-stop numbers can be difficult to understand fully, but to help you better understand them, remember that as the numbers rise, the settings on aperture decrease to half its size. In other words, each f-stop will allow 50% less or more light through your lens.
Aperture can be a difficult topic to learn, making it even more important get out and practice your photography at different f-stops to see what happens.