Metaphors belong to the larger class of symbols. The word symbol comes from two Greek root words meaning "to throw" and "together." The word symbol therefore means "to throw together." This is what a symbol does. When you cannot say what something is, you can say what it is like. A symbol throws together a subject that is not understood with an image that is understood in an attempt to throw light on the subject. It compares or throws together one thing that we do understand with something we do not understand in order to help us understand the thing that we do not understand. (Now, do you understand?) Symbols take us from a concrete, surface level of understanding to a greater depth of meaning. Metaphors do the same.