Depth-of-Field: Shallow and Deep

Shallow depth-of-field for portraiture; subject's face is in focus and background is blurred. Aperture is wide.
Extremely shallow depth-of-field allows for very selective focal point. Aperture is very wide.
Deep depth of field is used when most everything is to be in focus. Aperture is very small.

What is Depth-of-Field?

Picture
When you focus your lens on a subject, anything at that same distance from your lens will also be in focus. Things that are closer to or further from the camera lens will gradually - or quickly – get fuzzy. In other words, Depth-of-Field is the amount of your image before and beyond your focus point that will be in focus. Your camera's aperture controls the size of this in-focus zone.  The smaller your camera's aperture, the larger that depth of field zone is.
    Depth of field is determined by several factors:
  • Aperture/F-Stop
  • Lens
  • Subject Distance

Examples of Shallow & Deep Depth-of-Field:

Shallow Depth-of-Field.  Wide aperture. Low f-stop (f1.8).
Deep Depth-of-Field.  Narrow aperture.  High f-stop (f16).