Light is something we don’t think about, but almost everything that’s alive on Earth needs light for sight and energy. Human eats cow, cow eats grass, grass grows on light… you get the picture. Scientists have studied light for centuries, but still don’t fully understand it.
So what is light? An easy answer is “the first thing God invented”. A more detailed answer requires that I go physics on you, so here goes. Light is energy that takes form and moves as a wave. The wavelengths that we can sense with our eyes are collectively called the visible spectrum. Light is invisible to us until it strikes an object we are looking at, say a rose. The rose absorbs all of the wavelengths in light except red. This “red energy” bounces off the rose, enters our eye through a lens that focuses it onto the retina, which is packed with light sensitive cells called rods and cones. Certain cells are stimulated by the red wavelength and send signals to the brain, which interprets the color and tells you “that’s red”. I find it amazing that something invisible has all those colors hidden away, but rainbows are proof that they are all there.
What is not fully understand is how light moves through space as wave energy, but when it strikes an object (like the rose) it acts like a particle of energy called a photon. Light is loaded with unique features. It moves faster than anything else (186,000 miles per second) and is the universal speed limit: “thou shalt not go faster than light.” Astronomers use light speed as a measuring stick, giving distances to stars in “light years”. Light from distance stars is old. The light of the North Star (Polaris) left it 820 years ago to travel all the way to our eyes. Feel free to be awed.