A lumen is a unit of measurement used to quantify the amount of visible light emitted by a light source. It is a measure of the total amount of light visible to the human eye. The higher the number of lumens, the brighter the light. This is in contrast to watts, which measure the amount of energy used by the bulb. When comparing light bulbs, it's more accurate to consider the brightness in lumens rather than the wattage, especially with the increasing use of energy-efficient LED technology

. The lumen (symbol: lm) is the unit of luminous flux, a measure of the total quantity of visible light emitted by a source per unit of time, in the International System of Units (SI)

. For example, a 60-watt incandescent bulb is equivalent to about 800-850 lumens, and a 75-watt bulb is equivalent to about 1100 lumens

. In summary, lumens measure the brightness of a light source, and it's recommended to consider lumens instead of watts when choosing light bulbs to ensure you get the desired level of brightness