Aperture

The picture on the top was taken by a F16 which means that the aperture was smaller. The picture on the bottom was taken with an F2.8 and it relates to aperture because the background is blurred out and the focus is on the bird. The smaller the aperture the larger the F-stop, the higher the aperture the smaller F-stop. The Depth of field means the part of the picture that stands out more and the part that is mostly focused on.