Collage is derived from the French word, coller, which means to stick. A collage is a picture that is layered using images, paper, cloth, or other materials and applied to a canvas. This technique was often used by the Cubists and the Dadaists (Kurt Schwitters), who commonly used newspaper in these works.
so... collage vs. frottage
Frottage is from the French word frotter, meaning to rub. This technique is achieved by placing a piece of paper over a textured surface of some sort, and then rubbing back and forth with a pencil, picking up the uneven surface beneath. These effects on paper could then be cut up and applied to a collage. Max Ernst often used wooden surfaces in his work by applying this technique. Now, when you hear these terms, you will know what they truly mean.