Analogy

An analogy is a linguistic comparison of two objects that emphasizes the similarities between those two objects. For instance, a person can compare the structure of an atom (nucleus and rings of protons) with a solar system with a sun and orbiting planets. Analogies are often used as a means of describing a new object or concept by comparing it to something that is more familiar.

For example, Freud's three levels of consciousness are often described as an iceberg - the visible and tangible part (consciousness) is the part of the iceberg above the water, the subconscious is just below the water where you can still see it a bit, and the unconscious is the deeply submerged part of the iceberg.