Types of lights (Birn Chap 2.2)
Directional (distant, direct, infinite) light simulates a distant light source such as the sun where the light rays are coherent and parallel. A directional light tends to produce an intense quality of light with hard edges and no subtle changes in surface shading. Since a directional light is not easy to aim or confine to a local area, it is most useful as a part of your secondary or fill lighting.
Point (omni, omni-directional) light simulates rays shining out from a single infinitely small point in space in all directions. A point light can mimic the effect given an omni-directional local light source such as a light bulb and candle. When a point light is used with depth map shadow, a depth map is created in each of the axes directions (+x, -x, +y, -y, +z, -z), i.e., rendering tends to be time consuming
Spot light simulates light radiating from a single infinitely small point in space and has a cone of influence in a specific direction. Spot lights can be controlled conveniently to aim at a specific target.
  Ambient light is a non-directional light to simulate the diffused scattered or reflected light seen in real life. Often used as a secondary light source. Using an ambient light source alone to light up a scene make the objects in the scene appear flat.
Area light has a definable size. It simulates a realistic soft lighting distribution and realistic shadows that very from hard to soft. In Maya the area light is a 2-dimensional rectangular light
Volume light illuminates objects within a given volume, a sphere, cylinder, box, or cone. It gives a visual representation as to the extend of the light.

 

Characteristics of light sources
Type
 Position Ray's direction Size of source Shape of source Light fog (Maya)
Directional n/a parallel infinitely large n/a n/a
Point O omni-directional infinitely small n/a O
Spot O directional, confined in a cone infinitely small n/a O
Area O directional, radiating from the source area defined

defined

n/a
Volume O directional, radiating from the source volume and confined in the volume defined defined O