By this point, you probably know what F-Stop is. Are you using this setting on your digital DSLR to make your photographs look more professional? The F-Stop setting serves two primary functions, it dictates how much light gets into your lens and controls depth of field. For portraits, you will want a smaller number for your F-Stop (larger aperture) to allow you to get your subject in focus but not the objects in the background. On the other side of that spectrum, to have more objects in your photograph in-focus set your camera's F-Stop to a higher value (small aperture).
F-Stop, depth of field and aperture are all aspects of digital photography you will have to master as these control what is (and is not) in focus in your photographs. Used properly they allow you to achieve the blur in the background that you see in professional portraits or capture a large group scene, keeping everyone in focus.
A tip that Carl Weaver, a writer here at Bright Hub uses to remember how F-Stop works in digital photography is that at a F-Stop setting of f/4, 4 people will be in focus, while at f/32, 32 people will be in focus. As he says, it is not really an accurate statement but it does help you remember how the setting works and how you can use it to your advantage to take professional pictures.