watts tell you how much power a certain bulb uses/absorbs from the plug, and lumens tell you how much light that bulb produce (off those watts it uses)i really dont know anything about lumens and all that..
when you divide the lumens by the watts, you get an idea of how efficient a bulb is.
In my case:
1500 lumens / 25 Watts = 60 lumens per watt
*The bigger the number, the better*
you'll find many many threads covering this and every possible scenario on RIU about lighting