The buttons in the Light Type sub-palette determine the type of the selected light.
Sun
The Sun Light button defines the selected light as a sun light. Sun lights are lights which have no point source, so their rays are all cast in a parallel direction. You can use the Light Position window to specify the direction of the rays.
Point
The Point Light button defines the selected light as a point light. Point lights emanate from a chosen point in space, cast light in all directions, and have a finite radius of falloff. Choose the source point, and the falloff radius, using modifiers in the Lights Placement menu.
Spot
The Spot Light button defines the selected light as a spot light. Spot lights emanate from a chosen point in space, and cast light toward a chosen region of the canvas. Choose the source point, and the spot radius, using modifiers in the Lights Placement menu, below. Change the direction in which the spot light faces using the Light Position window.
Glow
The Glow Light button defines the selected light as a glow light. Glow lights emanate from a chosen point in space, and have a finite glow radius. Items within the glow radius are illuminated equally, regardless of the direction they’re facing.
Choose the source point, and the glow radius, using modifiers in the Lights Placement menu.
Radial
The Radial Light button changes the behavior of the selected light type. Normally, lights illuminate surfaces facing them. With the Radial Light button pressed, the selected light illuminates surfaces facing away from it, making it a good ‘fill’ light within a scene.
Radial lights do not cast shadows.
Reference Guide > Light > Lights Type