What is a rainbow? It is sunlight spread out into its spectrum of colors and diverted to the eye of the observer by water droplets, according to the National Center for Atmospheric Research and the UCAR Office of Programs. We call it a "bow" because it is a group of nearly circular arcs of color that all have a common center.
Here's a fun fact you probably never knew: When you face a rainbow, the sun is always behind you. The rain is in the direction of the rainbow. We traditionally think of a rainbow as having seven colors: red, orange, yellow, green, blue, indigo, and violet. Actually, there are more. A lot more--but the human eye can't see them.
The rainbow symbolizes God's covenant to never again destroy humanity with a flood. According to the Book of Genesis, "And God said to Noah, 'This is the token of the covenant which I make between me and you and every living creature that is with you , for perpetual generations: I do set my bow in the cloud, and it shall be for a token of a covenant between me and the earth. And it shall come to pass, when I bring a cloud over the earth, that the bow shall be seen in the cloud: And I will remember my covenant, which is between me and you and every living creature of all flesh; and the waters shall no more become a flood to destroy all flesh."
