Light is what you direct when you pay attention. It's what you concentrate when you concentrate. It's what gets yanked around when you are distracted.
It's also called Attention, Awareness and Sati. I like to call it Light (with a capital L) because it's like the beam of a flashlight in a dark room. Where it shines you see. Where it doesn't shine you don't see.
You direct your Light at experience-stuff. Sights, sounds, thoughts, feelings etc. Right now it is directed at the sight of these words on this screen, and at your thoughts about these words.
Light is mostly under the control of habits and reactions. So it's tricky.
It enlivens what it touches.