Light is everywhere in our world. We need it to see, it carries information from the world to our eyes and brains.
In the Book of Genesis, the Bible uses the symbol of light 263 times. Nothing is so commonplace, and yet so little understood, as light. The rainbow of colors that we perceive with our eyes is but a small fraction of light's wavelength. The Jews of Christ's time did not share our knowledge of invisible ultra violet light, infra red light, x-rays, gamma rays, radio waves or microwaves – mysterious properties that we gauge only with the help of sophisticated scientific instruments. To the Jewish way of thinking, light was simply the absence of darkness. To keep the light burning, they had to fill their lamps with oil and trim the wicks. They couldn't flip a switch, press a button or insert a battery; they had to attend to their lamps faithfully. Especially in their darkest hours.
Jesus uses the light cast from a lamp stand to to describe how his disciples are to live in the light of truth and love.