Three point lighting is the technique of using three lights to light a subject; a key light, fill light & back light. You will be able to make your subject stand out from a background and have more control over shadows.
The following video links will take you to chapters of a Lynda.com course which explains how to set up each of the three lights.
Key Light
The key light is the primary light used to light your subject from the front and slightly to one side.
Fill Light
The fill light is also positioned in front of your subject, on the opposite side to the key light. It is used to control shadows created by the key light and how much detail or definition you want on this side.
Back Light
The backlight is positioned behind your subject facing forwards so that your subject is highlighted from the background.