Type:
    Lights can be one of three types.  Point lights are a single point in space which emits light in all directions.  Directional lights are like the sun in that they emit parallel light in one direction only, no matter where they are placed in the scene (it's as if they're infinitely far away and have no falloff).  Spot lights are like point lights but their light is restricted to a certain area by a cone, much like a spotlight in a play or theater.

Diffuse:
    This button sets the diffuse color component of the selected light(s).

Ambient:
    This button sets the ambient color component of the selected light(s).

Specular:
    This button sets the specular color component of the selected light(s).

Constant Attenuation:
    This setting affects the intensity of the light.  Higher numbers make the light more dim.

Linear Attenuation:
    This setting affects the intensity of the light as objects get further away from it.  This atenuation has a linear effect, i.e. an object twice as far away will receive has a much light.  Higher numbers make the light more dim.

Polynomial Attenuation:
    Same as linear attenuation, except the effect is amplified so that moving twice the distance away from the light will cause the object to recieve several times less light, depending on the number entered.

Spot Exponent:
    This setting adjusts how the light of a spot light fades as it gets further from the center of where the spot light is aiming.  Higher numbers make the light fade quicker as it goes from the center to the edges.  Play around with it to find a good value for the effect you're trying to acheive.

Spot Angle:
    This setting adjusts how wide the angle of a spotlight will be.