Satire makes us laugh because it takes a societal or political topic and mocks it. Jonathan Swift wrote "A Modest Proposal" in 1728 -- and it turned into a seminal work of satire for several hundred years. In his writing, Swift proposes that Ireland can solve the economic problem of poor children by selling them to the upper-class as food. Cannibalism then serves as a hyperbole for the general attitude toward the poor in Ireland during Swift's time.
Good satire informs its viewership as well as entertaining them by making something absurd. Also, satire protects its creator because he does not explicitly state his opinion. The satirist induces the audience to think about the occurrences and social mores that often go unnoticed -- by placing characters in unusual situations. For example, Aldous Huxley often puts characters with modern traits in a futuristic setting. This is funny because humans tend to laugh when they see an incongruous and non-serious situation, such as someone falling down, according to "Scientific American."
Sarcasm and irony pervade most satires. For example, in the movie "The Truman Show," the audience knows the main character lives on a movie set, but that character doesn't. However, a writer often employs several types of wit to make his audience laugh, such as parody and double entendre. For instance, Weird Al Yankovic took the Michael Jackson song "Beat It" and turned it into "Eat It," a song about an obese man.
Just like most other literature, satire constantly evolves. The satire of the ancient cultures contained far fewer political attacks than the satire of the 21st century. Some television shows, such as "The Daily Show With John Stewart" and "The Colbert Report," almost entirely ridicule contemporary politics. However, satire can maintain relevance for centuries if it pokes fun at human behavior.
Good satirists usually present their material in a deadpan manner -- as if they truly believe it -- then go on to ridicule the premise with absurdity. Sometimes a writer needs an innate sense of humor to make good satire. The writer E.B. White once said that dissecting humor is like dissecting a frog -- it kills the essence of it.