Depth of field is a phrase used in photography to describe the zone within a camera lens that appears sharp. The depth of field varies based upon the camera being used, aperture and focus.
Depth of field can be described as shallow or deep. The term "shallow" is used when the items within a narrow range are the only sharp ones in the picture. A deep depth of field is when a large part of the image is in focus. Sometimes, a shallow depth of field is preferable to a deep one, as when the photographer wants to blur out background images to draw focus on something in the foreground.