Lumens measure the total amount of visible light emitted by a source, i.e., brightness. More lumens means brighter light. Color temperature (measured in Kelvin, K) describes the color appearance of the light, from warm yellow (2700K) to cool blue-white (6500K). These are completely independent specifications: a 100W LED high bay can be 10,000 lumens at 3000K or 10,000 lumens at 5000K, same brightness but different color. When selecting lighting, first determine the required lumens based on the space size and application (lux level needed), then choose the color temperature based on the desired atmosphere and function. Confusing these two specs is a common mistake that leads to disappointing lighting results.