It’s the recognition of the ontological correspondence between a given thing, rather natural, or accessible to us (water, a tree, a bird, the number two, a cross, etc.), and something else that transcends our reach. This correspondence is based on the link that crosses all states of existence: corporeal, psychic and spiritual. In practice, symbols, due to their anagogic potency, whether reflected upon or acted upon (rites), lead to higher states of understanding.