An analogy is a mapping of Attributes and Behaviour between two domains. Once Niels Bohr identified the mapping between the atom and the solar system much of the knowledge and behaviour understood of the solar system could be used to expand our knowledge of the atom.
Analogies lie at the heart of great advances in humankind but they are also the building blocks of our mundane, everyday intelligence. For example we can pilot a small motorboat when we have only been trained in driving a car as we will naturally identify the analogy between the two.
Hollyoak and Thagard identify three broad constraints in how we choose analogies;- Similarity; structure; and purpose.