Lights illuminate objects. If your scene contains no lights, then it renders entirely black (unless, for example, you are using shaders with incandescence). You can also use lights to create special optical effects (for example, halos, lens flares, or fog).
There are seven different types of lights. There is also a tool for creating default lighting for a scene.
Point lights are like
incandescent light bulbs—they cast light in all directions. See Render > Create Lights > Point 
.
Spot
lights cast light in one direction only, emanating from a point
in a cone. See Render > Create Lights > Spot 
.
Directional lights are directional source lights
that have color, intensity, and direction, but no obvious source
in the scene. See Render > Create Lights > Directional 
.
Ambient lights are similar to point lights except
that only a portion of the illumination emanates from the point.
The remainder of the illumination comes from all directions and lights
everything uniformly. See Render > Create Lights > Ambient 
.
Volume lights define a closed volume in which
objects are illuminated, and nothing outside the volume is directly
illuminated by the light. See Render > Create Lights > Volume 
.
Linear lights are one-dimensional line-like lights
similar to fluorescent tubes). See Render > Create Lights > Linear 
.
The Create
defaults tool sets the default lighting for a scene.
When you select Render > Create Lights > Create Defaults 
, an ambient light and a
directional light are automatically created. Their orientation and
position are pre-defined and their values are based on each light’s
default options.
.