Satire is defined, by the Oxford Dictionary, as:
The use of humour, irony, exaggeration, or ridicule to expose and criticize people’s stupidity or vices, particularly in the context of contemporary politics and other topical issues.
There are three classes of satire:
Horation - satire which mocks normal society. This is a gentle form of satire, which invites the audience to laugh at/with themselves - and by extension, the folly of society. Examples: South Park, The Onion, Ig Nobel Prize
Juvenalian - satire which mocks public officials. Here the ideas and opinions of political representatives are portrayed as evil. This is therefore an extreme form of satire, which often employs sarcasm and irony. Juvenalian satire is used to provoke change. Examples: George Orwell's 1984 and Animal Farm,
Menippean - satire which mocks attitudes (especially those of close-minded, bigoted persons). Examples: Gulliver's Travels, The Hitchhiker's Guide to the Galaxy, Alice in Wonderland
Stand up comedians, or 'revue' productions, often make use of satire - exaggerating an idea or argument until it becomes ridiculous.
There are a number of satirical devices that can be employed to further satire. These include humor, irony, sarcasm, word play, parody, and many more.