What is it called when a writer or speaker says one thing but means something completely different?

I think it is called Irony... not entirely sure...

Delegates: representatives who cast votes at a political party's national convention. binding: if a primary or caucus is “binding” that means the delegates won in that contest are legally bound to vote for a particular candidate at the parties national convention.a primary is a preliminary election used to determine a party's nominee for a specific office. the winner of the party's caucus, or primary, wins the party nomination for that state. then the delegates meet at their party's national party convention, which is a formal gathering of all party delegates from all states.

You need writing an informational letter?