Colour temperature generally refers to the colour of light. The temperature is measured in a scale known as Kelvin (K). Unlike our eyes that naturally adjust to different colour shifts in light, cameras do not nessecarily do the same. Now most cameras now have auto white balance, but can often and easily be fooled. Auto White Balance will not work well with off camera flash or certain artifical lighting sources.
Here is a quick guide to get you started:
1,700 K Match flame
1,850 K Candle flame, sunset/sunrise
2,700–3,300 K Incandescent lamps
3,000 K Soft (or Warm) White compact fluorescent lamps
3,200 K Studio lamps, photofloods, etc.
3,350 K Studio "CP" light
4,100–4,150 K Moonlight
5,000 K Horizon daylight
5,000 K tubular fluorescent lamps or cool white/daylight compact fluorescent lamps (CFL)
5,500–6,000 K Vertical daylight, electronic flash
6,200 K Xenon short-arc lamp
6,500 K Daylight, overcast
6,500–10,500 K LCD or CRT screen
Here is a more in depth and techincal analysis.