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. Symbols take us from a concrete, surface level of understanding to a greater depth of meaning.
Metaphors do the same.
Thinking of life as a journey is a metaphor. We can think of life's journey in many different ways. From our beginning life is taking us to a destination with challenging adventures along the way. Life may be seen as an ocean voyage across unknown depths where storms occasionally toss us about as we seek the safety of calm shores. An old bluegrass song tells us that life is like journeying on a mountain railway with hills, tunnels, dangerous curves and the need of a brave engineer.