You may or may not be able to understand the definition of color temperature, but you know it when you see it. The two luminaires in this photo both have compact fluorescent lamps in them.
Saving energy = saving money = good.
Mismatched color temperatures = bad.
The one on the left is a cooler color temperature than the one on the right. A cooler color temperature has a higher number, measured in Kelvin, while a warmer color temperature has a lower number. These two are around 3000K and 2700K. When shopping for replacement lamps, make sure to get consistent color temperatures, and decide ahead of time whether you want a warm color like incandescent or a cooler, "whiter" light.