What Does Aperture Do?
Aperture affects the depth of field- how far back you see while objects are still defined. A sharp aperture creates a sharp image, you can see the main focus, and the background objects. A shallow aperture creates a blurry background, you can see the main object clearly only, and the background is out of focus.
The higher the aperture number, the sharper and more focused the image will be. It will also let in a lot less light. The lower the aperture is, the blurrier the background, and a more exposed image.