The Three Types of Irony

Dramatic Irony: When the audience is aware of something characters in the story are not. 
This creates tension for the reader! It's like when you're watching a scary movie, and you see the killer behind the main character and you want to scream, "LOOK OUT!"

Verbal Irony: The term verbal irony refers to the use of vocabulary to describe something in a way that is other than it seems.

Verbal irony is often a comment that conveys a different meaning than what it may seem to be.

Example: "This music sounds as good as steel hardware nails clanking against each other in a kitchen blender."

Situational Irony: When something entirely different happens from what audience may be expecting or the final outcome is opposite to what the audience is expecting. 

It is also known as irony of situations that generally include sharp contrasts and contradictions.