Light Types
Then of course, there are the lights themselves, the things you'll likely be working with the most. Despite game engines and 3D programs having a lot of differences between them, lights are usually pretty similar in what types there are, how they are set up and how they work across the board.
While it's a bit of an oversimplification, light types usually fall into the following types:
Point Lights: Light that comes from a single point in space, and spreads out in all directions. The simplest type of light, but the one you will probably use the least often, especially for casting shadows.
Spotlights: You will probably use these the most. A spotlight lets you control where the light is hitting your scene through the use of a light cone, that can be made wider or more narrow.
Distant Lights: A distant light (sometimes called parallel light) is usually there to act as the sun (or moon). It does not have a cone like a spotlight, and all rays are parallel. Where a distant light is placed in the scene is unimportant, the only thing that matters is its rotation.
Area Lights: These are generally not used in real-time lighting, and are more likely to be used when you are using lightmaps and baking the lighting. It's a light that has a large, soft surface area, and gives off the softest shadows.
Skylights: Some game engines also have "skylights", which are normally used to simulate soft/fill light from the sky.
There are also sometimes "specialty" lights that do something specific, and don't just light objects in the normal sense. These include things like:
Eye reflection lights: These are more likely used in cinematic lighting, and give a tiny bright reflection in a character's eyes. Without these, eyes can look "dead" if the main lights in the scene are not causing reflections where you'd like to see them.
Light Rigs: In some games, lighting "rigs" may be used to speed up the lighting process or allow for more lighting continuity by using rigs. Rigs can be loaded into a level or a cinematic and either parented to a character or left freestanding. They usually consist of a key light, a rim light, and a fill light, and sometimes have secondary lights as well.
Regardless of the light types you work with, most of them share a number of qualities you'll be adjusting on a regular basis, including:
Color: The RGB values of the light
Intensity: How bright the light is. In addition, many systems allow a simple animation type to lights, so that they can "flicker" as seen on candles, campfires, etc.
Light Falloff: Also sometimes called Attenuation. How rapidly the light falls off from the source. This is usually stated as either Linear or for a more realistic look, Quadratic. On a more technical note, the Inverse Square Law states that the intensity of light is inversely proportional to the square of the distance. Sounds fancy, eh?
Here's a page that shows different falloff effects.
Shadow "Hardness": The smaller the source of light, the harder the edges of the shadows. As the light source becomes larger, the shadows become softer.
Shadow Color: In some programs you have the ability to force the color of the shadows, so you could for instance, make shadows warmer or cooler than they normally would be.
All of these things will vary slightly (or sometimes greatly) from engine to engine.
