Three point lighting consists of the key light the fill light and the back light and is used in the media to light the subject according to what they are doing.
The key light is used as if it was light coming form the sun on a cloudless day, a hard light which will create shadows on and around the subject but will show off all the features of it .
The fill light is more like the sun shining throw a cloud to defusing the light which fulls upon the subject, a soft light which will leave the subject less defined but it will create softer shadows.
The back light Is used to create a halo around the subjects body, separating them from the background and drawing more focus to the subject. In film and T.V industry they might only use this light so that we wont see any of there body feathers, only an outline of it. This is used on crime shows such as crime watch when someone is telling a story of something that happen to them, its used so no one will know who they are so they don't get targeted later after the show has be broadcast.
The background light is used to create an even light on the background so that there are no shadows, and makes it so the background wont be more shadowed on one side while more lit on the over. by using all these lights together you will get 4 key lighting.
High key lighting is used to light a subject and show off there features but also gives the skin a more smooth look by reducing dimples and other defections, this is commonly used for interviews with famous people or profile pictures for acting adjacency.
Low key light is where you Just use a key light to create shadows over the face of the subject giving them a more serious/dramatic look.this is also used as a profile picture for an acting adjacency or in films when they want to give more feeling to a-close up of an evil characters face.
Limbo is also another term used for lighting, it means only light the subject and for everything else to be black/dark. this type is used for adjacency, the cover of an album or for a shot in a horror film where someone is alone in the dark, giving the audience an unerring feeling of not knowing where they are, or whats behind them.
Colored light is when you place a colored sheet of plastic over the light to create a different feel to the shot. this is used when they want to give the shot a more interesting look and feel to it and is most commonly seen in si-fi movies.