Expressionism- an art movement focused on depicting emotion rather than a sterile, accurate representation of reality. Though it is usually dated as to have begun in or around 1905, impressionists such as Vincent van Gogh and Paul Gauguin are often credited as pioneers of the Expressionism movement.
Abstract Expressionism- a painting style that generally involves rapid, forceful strokes on large canvases. The general goal of the Abstract Expressionist is to capture emotion on canvas. These paintings are usually done spontaneously in an attempt to tap into the subconscious mind of the artist. Abstract Expressionism is more about the creative process then the finished product.
Here are examples of this method as executed by Jonas Gerard:
Jonas Gerard Live Painting
Jonas Gerard Interview
Jonas Gerard - Explaining and Demonstrating the Method
And a video clip of another abstract expressionist:
Abstract Expressionist Svein Koningen