These are tricky and native English speakers will argue about them. Wikipedia is a good source. Very roughly: "Irony" (sometimes) means intentionally saying saying the exact opposite of what is meant. Your friend says "Turn left here, I know a good shortcut." Ten kilometers later you come to a sign saying "Bridge out, road closed." You say to your friend "Oh, yes, that was a GREAT shortcut." "Sarcasm" means an intentionally cutting, bitter, or insulting remark. Often, it will be ironic. Often, it is convey as much by manner and tone of voice as by the words used. For an example of sarcasm that is not ironic: you come to work on Friday wearing blue jeans, and someone who doesn't like you says "I see you're wearing your BLUE JEANS today." It's true. You ARE wearing blue jeans. But the voice and manner suggests that he thinks there's something wrong with you or how you are dressed. "Satire" means some kind of literary work--a play, a book, a comedy sketch--whose purpose is to attack something by making fun of it. It makes the audience laugh but the audience senses the author's anger. A classic example would be Jonathan Swift's essay, "A Modest Proposal for Preventing the Children of Poor People From Being a Burthen to Their Parents or Country, and for Making Them Beneficial to the Publick." He is angry at the callous attitude the government had toward the poor in Ireland. He expresses this anger by pretending to be one of those people, and arguing that the Irish ought to sell their children as food for the rich: "a young healthy child well nursed, is, at a year old, a most delicious nourishing and wholesome food, whether stewed, roasted, baked, or boiled; and I make no doubt that it will equally serve in a fricasie, or a ragoust."