What a strange thing light is. It gets into corners, shines brightly and illuminates. You can see it at a distance even if it’s millions or billions of miles away. It might be made up of packets of energy (photons) or waves. It has different wavelengths for different colours and is part of the electromagnetic spectrum. It moves at the speed of light in a vacuum. But slower in an atmosphere or travelling through another medium like water or glass. It can be refracted (bent) depending on the wavelength which is why Sir Issac Newton found it was made up of a spectrum of rainbow colours when he passed a beam of daylight through a prism in a darkened room.
Apart from the scientific details which I only have a sketchy knowledge of, there are lots of phrases that are used in English :
Shed a light on it, light of my life, light at the end of the tunnel, thunder and lightning, the light fantastic, by the light of the stars.
Light is a fascinating subject.