. The simplest way for me to explain this is besides the housing itself it’s the spectrum. The human eye prominently sees Green (the 500 nm part of the spectrum). Plants can and do use the Green part of the spectrum, but also need and utilize the Blue (380 nm - 490 nm), Red (620 nm - 700nm), and Far-Red (730 nm) parts of the spectrum
The Blue is good for root growth, the Green is great for deep penetration of the leaves and the overall canopy, the Red is good for growing leaves, and the Far-Red helps to grow larger plants faster and aids with blooming faster for most plants. So, our LEDs are not just the Green part of the spectrum that our eyes see, but rather a full-spectrum LED that plants need with the addition of Far-Red.