Depth of Field
This is the third episode in my "Photography in (under) 90 Seconds" (P90) series.
Depth of Field = Range of your photograph that appears to be in focus. You can control this by varying the aperture of you lens.
In addition to watching this video, I recommend going out and experimenting with different apertures yourself in order to get a 'feel' for how each aperture setting changes the depth of field in your images. For the beginner, the easiest way to experiment with this is to set your camera to Av (aperture priority). In this mode you set the aperture and your camera will set the appropriate shutter speed to get a good exposure. If you want a shallow depth of field, you will also need a 'fast' lens; i.e., one that has a maximum aperture of something like: f/1.4, f/1.8, f/2, or even f/2.8. Lenses of this sort are often very expensive, but each camera maker offers a fast 50mm lens for relatively cheap (compared to other lenses). Good luck.