Lumens: measures light output. The higher the number, the more light is emitted.
Lumens per watt (lm/W): measures efficiency. The higher the number, the more efficient the product.
Watts: measures the energy required to light the product. The lower the wattage, the less energy is used.
Correlated Color Temperature (CCT): measures white light color. “Cool” colors have higher Kelvin temperatures (3600-5500 K); “warm” colors have lower color temperatures (2700-3000 K). Cool white light is usually better for visual tasks. Warm white light is usually better for living spaces because it casts a warmer light on skin and clothing. Color temperatures of 2700 to 3500 K are recommended for most general indoor and task lighting.
Color Rendering Index (CRI): measures the effect of the lamp’s light spectrum on the color appearance of objects. The higher the number, the truer the appearance of light on objects. Incandescent lighting is 100 on the CRI.