The sun has a certain combination of colors at different brightnesses. Light bulbs that appear white may have different blends of colors. Most flourescent lights only use a few colors. Some people prefer the light from full spectrum flourescent lamps because it feels more comfortable on the eyes. Regular flourescent lamps can be harsh and glaring.
Incandescent lamps are by nature closer to full spectrum.
UV light is the invisible light that is contained in sunlight and some light bulbs. It causes tanning and can cause eye damage. It is not helpful for winter blues. That is why a trip to a tanning booth isn't a replacement for a good bright light product. Most light product manufacturers ensure that UV light is filtered or not given off by their bright light products.