In Blender, lights are called "lamps." Select the only lamp in your scene and then look at the Outliner to see that the Object is named "Lamp." Expand the hierarchy to see the datablock named as "Spot" (Figure 1).
Figure 1: Outliner with default Lamp
The Outliner default name is a litlte confusing; the default lamp in our scene is actually a Point lamp, as you'll soon see. In order to better see how the different lamps render, delete the default cube and add a sphere and a plane. I've scaled up the sphere by 2, did a Shade Smooth on it, added a Subdivision Surface modifier to it and moved it up on the plane. Then I positioned the camera on the sphere.
With the lamp selected, click on its Object Data icon at the top of the Properties panel (the icon will look just like the datablock in the Outliner). Again, the field at the top allows you to rename the lamp datablock. You can also access the lamp datablock list by click on the icon to the left of the name field. The Preview will give you a rough idea of how the light is distributed.
Below the Preview is the Lamp section. This section is common to all the types of lamps Blender has to offer. First notice the string of buttons at the top of this section. These are the lamp types: Point, Sun, Spot, Hemi and Area. You may change your lamp to any type at any time.
General Lamp Properties
The properties in this section will slightly differ, depending on each light, but there are a few properties that are common to each lamp type. These include: Light color (color swatch), Energy (intensity of lamp) and the checkboxes for Negative, This Layer Only, Specular, Diffuse.
"Negative" will suck light out. "This Layer Only" is a simple way to restrict the lamp to only render on the scene layer it's on. "Specular" is on by default and will render highlights if there's a specularity value on the material. "Diffuse" is on by default and will render surface color if there's a diffuse value on the material.
The Point lamp is the default lamp in your scene, as indicated by the Point button being activated. It has additional falloff properties, as well as a Shadow section (Figure 2).
Figure 2: Point Lamp properties
A Point lamp is also known as an "omni-directional" light. It radiates light in all directions, like a light bulb. It only depends on location, as rotating it or scaling it has no effect. Render your scene to see something similar to the figure below (Figure 3).
Figure 3: Point Lamp and render
Next, click on the Sun button (just below the Preview) to change your Point lamp into a Sun lamp (Figure 4). A few options change as you do this. First of all, the Falloff properties disappear.
Figure 4: Sun Lamp properties
A Sun lamp is also known as a directional light. It's not dependent on position and can be placed anywhere with the same effect. Therefore, any lamp that is not dependent on position should have no Falloff options. The Sun lamp has shadow options, as well as Sky & Atmosphere options. Render your scene to see that the Sun lamp renders even lighting in one direction (Figure 5).
Figure 5: Sun Lamp and render
Let's now change the Sun lamp into a Spot lamp by again click the Spot button (Figure 6). The Falloff options return. The Spot lamp also has options for its spot shape, as well as shadow options. This is the one lamp where the Preview has the most use, as there's a more defined shape to the light.
Figure 6: Spot Lamp properties
A Spot lamp is also known as a spotlight. It depends on both position and rotation. If you go into wireframe mode (hit "Z"), you can see a better representation of the lamp. Render your scene to see its effect (Figure 7).
Figure 7: Spot Lamp and render
Now, change the Spot lamp to a Hemi lamp (Figure 8). The Hemi lamp has the least options of all. In fact, it only has the general properties common to all lamp types.
Figure 8: Hemi Lamp properties
A Hemi lamp is like a Sun lamp in that they both depend on direction but not position. A Hemi lamp, however, will not cast shadows (hence no shadow options). It will also fill the shadow areas and produce even lighting everywhere within its "hemisphere." Render your scene to see its effect (Figure 9).
Figure 9: Hemi Lamp and render
Finally, change the Hemi lamp into an Area lamp (Figure 10). Area lamps have Falloff options, lamp shape options and shadow options. They also tend to take longer to render, depending on your scene.
Figure 10: Area Lamp properties
The Area lamp is most like a Spot lamp in that it depends on position and rotation. You also have the ability to change its shape, but the shape is a square or rectangle. Think of it like a "rectangular box of light" with the option of having falloff (Figure 11). Some use Area lamps for windows, sizing the lamp to the dimensions of the window.
Render your scene to see its effect. If it's blown out, like shown in this figure, lower the Distance value to adjust its falloff (Figure 12).
Figure 11: Area Lamp and render
Figure 12: Area Lamp with tweaked render
Add a Lamp
Now that you've seen each lamp's properties, what if you want to add a new lamp to your scene? It's pretty easy: just hover in your 3D view, hit Shift + A to bring up the Add menu, choose Lamp and then choose your type (Figure 13).
Figure 13: Add a Lamp