According to the WebMuseum's glossary, surrealism is a 20th-century literary and artistic movement that attempts to express the workings of the subconscious by fantastic imagery and incongruous juxtaposition of subject matter.
You may be familiar with the work of principal surrealist artists Rene Magritte, Salvador Dali and Joan Miro. For more resources, check out MuseumSpot's Reference category, where you'll find artist information, dictionaries and more.