1. The body part that you can relate aperture is your eyes because your eyes has the power to blur out the background in something that you are focused about. And like a camera the amount that your eye pupil is open the more light passes through.
2. The smaller the Aperture the larger f-stop is. But the larger Aperture means smaller the F-stop is 



Camera Aperture is at F16 or higher 

3. So the smaller aperture the more of the background  is blurred out. But the larger the aperture the background is blurred out even less

   

   Camera Aperture is at F2.8