Luminance units

I'm trying to read lights specifications but cant figure and compare the unites

I saw: lumen, MCD, candle lightת Watt and others units.

Can someone point me to the definitions of the common units and how to convert between them?

Lumens are the SI unit of luminous flux (ie the apparent brightness) as perceived by your eyes. Watts are a measurement of radiant flux which is the actual power delivered.

Check out http://en.wikipedia.org/wiki/Lumen_%28unit%29 for details.