Symbols are more complex and have greater imaginative resonance
Icons stand for an object by resemblance
Metaphor is use of an image for something it does not literally denote
Allegory is often symbolic representation of a moral or political concept
Irony involves a twist of language, often by using the opposite of what is meant
Parody is a humorous or satirical imitation
The Oxford Dictionary definition of a metaphor is the
"application of a name or descriptive term or phrase to an object or action where it is not literally applicable".
In this way, the metaphor is itself a semiotic sign providing meaning obtained from what is referenced. More than that, the metaphor adds to other communication by providing the association of a meaning to an unfamiliar object rather than only a familiar one. This extra ability of metaphor adds an extra layer to sign-object meaning model. Extending from the word metaphor, when we introduce the concept of a "family tree" to someone for the first time, we allow the pre-existing identity of a tree to help provide meaning to the way we can look at family history. The metaphor acts as a super-interpretant, providing an interpretation where none would normally exist. This super-interpretation makes the metaphor a vital tool in computer interface development as it can be used as a powerful sign for the audience viewing it.