 It's just the wavelength of how deep they go into the skin. So I guess to touch up on red light really quick, red light therapy, it's good because it goes so much deeper into your skin than what the sun could do. The sun can only give you the UV rays, and that will go to your skin and maybe just slightly under. But what's so great about these other therapies, like red light, it has the ability to go deep into your skin