Middle gray is the same color shade as a gray crayon or pencil. It is not too dark like black or too light like white. It is just in the middle. Middle gray is very important in photography because it helps the camera to know what color and brightness levels should be used for the picture. It acts like a reference point for the camera's meter to make sure the colors in the photo look right. Think of it like baking a cake. You need a certain amount of flour to make the cake right. Middle gray is like that amount of flour for the camera to make good pictures.