Depth of field is the amount of distance between the nearest and farthest objects that appear in acceptably sharp focus in a photo.
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image.
When it comes to how the aperture effects the depth of field, when
the hole is at its biggest, the number is low and so is the amount of focus width. When the hole is at its smallest, the number is large and so is the focus width.
As you can see in this image, the depth of field has changed throughout. On the left you have large aperture (hole) which means the depth of field is small and so is the number (f4.0). On the right you have a small aperture (hole) which means the depth of field is very large which means everything is in focus it also means the number is larger (f22.0).
These are just a few of the images i have taken today, as you can see in all of them the images on the left side of the trio have got a larger aperture (hole) there for these images have a smaller depth of field and seem to be more blurry (f2.0). The images on the right of the trios however have a smaller aperture (hole) there for these image have a larger depth of field and are\trying to be in all focus (f22.0) . Lastly the images in the middle of the trio are in-between the aperture range.