Jung believed that symbols are created spontaneously by the psyche. Our dreams are constituted entirely of symbols, which Jung differentiated from signs. Signs include names, emblems or images that point to something known. For instance, the name ‘wife’ is a sign that points to a known person, to this man’s marriage partner. But symbols operate on a different plane, and point to something as yet unknown. The ‘wife’ in a dream points to an interior, psychic reality that does not correspond with outer reality. For Jung, the same word can function as a sign or a symbol, depending on whether or not it is being used by the unconscious to point to internal realities.
A sign is obvious, manifest and can be understood by reason. A symbol, however, is mysterious and can only be discerned by intuition or poetic understanding. It is symbolic knowledge that Jung is concerned with, and he is attracted to what is deep, profound and obscure. The study of signs leads to semiotics, linguistics and discourse analysis. The study of symbols leads to mythology, religion and philosophy. For Jung, the unconscious is not speaking about the external social world, but about the internal psychic plane, which cannot be known directly. It is real in its own right, though not in the sense that we usually designate as real, and symbols are the nearest we can get to approaching this unknown realm.
Jung’s Wiki Page