Wide Depth Of Field
This picture shows a wide depth of field which means it is taken on a lower aperture setting. This lets more light into the lense creating more distance in terms of focus on what you're photographing. As you can see in this picture that I took of a wasp everything that isn't directly in focus is blurry. Therefore the lower your f-stop the less in focus and more blurred everything else that isn't in focus is.
Narrow Depth Of Field
A picture with a narrow depth of field is the complete opposite in that instead of one part of a photo being in focus everything is more sharp and there looks like there is less distance between what is in the photograph. This is because a higher f-stop is used meaning less light goes into the lens.