Depth of field is most easily explained as the distance from your camera where something is in focus. You might have a flower 40 cm away from your camera, for example. If the background is 6 meters away, and both are in focus, you have a large (or ‘deep’) depth of field. If only the flower is sharp, and the background is blurry, you have a low (or ‘shallow’) depth of field.
For maximum impact of your photos, ensure that your foreground is in focus whilst your background isn’t. Depth of field is affected by a few different things, but for an incredible camera-phone like the Nokia N8, the distance from your lens to the subject is most important, as you already have a gorgeous, incredibly bright f/2.8 lens to play with.
The trick to achieving a narrow depth of field, is to zoom out completely and go as close as you can. Use your shutter release button on the side of the camera rather than the one on your screen: You can press this button half-way to make your camera focus. Wait for a small green rectangle to show up your screen. If a yellow rectangle shows up, try again. If you go really close to your subject, you may have to turn on the Macro mode (signified by a little flower, under your ‘focus’ options) to help your camera focus.
Once you’re happy with your focus and composition, press the button all the way down to take your photo. It’s incredible: it may take a little bit of practice to get used to the ‘focus first, then take the photo’ technique, but it’s worth it: by using a shallow depth of field you can get that ‘professional photography’ feel with the camera you carry with you everywhere!