Dadaism
Dadaism was an artistic movement, shaped as an aftermath of the calamity of The World War First. It ridiculed the evil practices of the war through mock-ups, cut-up poetry, sound poetry and collage. It's naming scheme is obscure.
Surrealism
Dadaism did not last that long, but it formed another movement, Surrealism which originated in 1924 and defined as "psychic automatism in its pure state, by which one proposes to express - verbally, by means of the written word, or in any other manner - the actual functioning of thought." as André Breton points out. Surrealistic art is the product of a subconscious mind. Surrealistic artists follow Dr. Sigmund Freud's statement of the unconscious state of dreams, that the artistic fulfilment of desires in such state relish human psyche.
Techniques
Exquisite Corpse
This technique sounds like a game in which a sheet conceals a player's writing or sketch and other artistic players are asked to complete the drawing or writing.
Frottage
This technique deals with the canvas which is placed on a wooden surface and it is pencilled to copy the wooden texture.
Automation
Automatism was the chiefly used technique to compose poems during that movement and is still popular till now. It deals with the harmony of pen and mind. Poems are composed without keeping in view their rhyme scheme and rhythmic pattern.