Depth of field is the distance between the nearest and the furthest object giving a focused image. The smaller the stop in the lens, the greater the distance in front of the camera which means the objects will look sharper. The distance measures from the nearest to the furthest sharp point, is the depth of field. The larger the stop in the lens, means the whole picture will be in focus.
Aperture adds to a photograph by blurring the background and brings the main focus into light. Aperture is a hole in the lens which light travels through. As you increase the aperture you decrease the amount of light passing through the lens. The quality of light affects the amount of the picture that appears sharp and in focus, this is the 'Depth Of Field'.