What is Aperture?
The aperture is the point were it is bigger or smaller depending on how much light travels through. It is a focal length that helps the camera focus. The aperture is larger when the depth of field is small. This also creates a better image so it is all over exposed .
This picture has a large aperture. This is effective because the light is slightly blurred out but it make the picture its more efficient.
This is a small aperture. Which is a large depth of field as the bigger your aperture the smaller your depth of field. this is effective as you can see the whole scene.
More Examples
This shows different apertures of the same daisy plant.