What's the difference between watts and lumens?

Watts indicate how much electricity is used by a bulb. Watts are not an indicator of a bulb's brightness.

Lumens measure the amount of light a bulb emits. A bulb's lumens let you know how it performs as it comes out of the light source.

For comparison, a standard 60-watt indandescent bulb and a 9-watt LED will both emit about the same 750-850 lumens.