[brucepick]

Degrees K is a way to measure color "temperature".
Lower numbers are "warmer", more yellow. Higher numbers are closer to neutral white, and look blue in comparison to the regular bulbs that are around 48000K. It's all relative.

Lumens - as mentioned earlier - is a measure of light output. I'm trying hard to remember - I think it's measured at the surface the light arrives at. So a plain bulb with no reflector will deliver fewer Lumens to a location than the same bulb equipped with a well designed reflector.

There's another topic where higher color "temperatures" supposedly help you see better, assuming equal Watts or Lumens.