LED ligthing and lumens

What is a lumen, I thought watts was a measurement of brightness?

Lumens measure the total amount of light emitted by the bulb while watts measure the amount of power consumed by the bulb. Watts do not tell you how bright the bulb is, lumens do. It is easy to estimate how bright an incandescent bulb is; the higher the wattage rating, the more light emitted.

Back of the napkin lumen calculator

Old incandescent 60 watt bulb = 800 lumens