What is Large Depth of Field?

The Basics:

A large depth of field (DOF) means a greater range of the scene is in focus, as opposed to a shallow depth of field when only part of the scene is in focus. To achieve a large depth of field, you would use a small aperture. Landscape photography generally uses large depth of field to make sure close objects as well as objects further away, are sharp and in focus.
See Depth of Field for more information.