Depth of Field is how much of an image is in focus; it is the distance between the closest and furthest object within the photograph. The control over the amount of light let in by your camera. There are two different aspects included in this technique named Focus Points and Aperture. Aperture plays a big role upon choosing your Depth Of Field as a Large Aperture gives it a shallow DoF, and a Small Aperture gives it a deep DoF.
Shallow Depth Of Field
Small Depth Of Fieldis when you have a small zone of your photograph in focus.
Medium Depth Of Field
Medium Depth Of Field is when there is an equal amount of the picture in and out of focus.
Deep Depth Of Field
Large Depth Of Field is when you have a vast amount of your photograph in focus.