Irony refers to a situation which outcome is totally different from the one expected, or to words that have a meaning beyond their original one in order to say something without offending another person. Often, irony can be comical, and sometimes it can be bitter.
The best example of irony is C. A poorly written book that is full of clichés and weak characters is called Stories of Genius. When reading the title, the reader has an expectation, but the content of the book ends up being completely different from the one imagined.