Short answers, pulled from the story.
The year 1905 marked a turning point when four German artists formed Die Brücke in Dresden. Ernst Ludwig Kirchner led this group though they did not use the word Expressionism themselves.
This group existed together for only one year until 1912 after forming in Munich in 1911. They reacted against French Impressionism which emphasized visual appearance over emotion to portray subjective interpretations using powerful colors and dynamic compositions.
German cinema produced notable examples like Robert Wiene's The Cabinet of Dr. Caligari released in 1920 and Fritz Lang directed Metropolis which arrived in 1927. Paul Wegener created The Golem: How He Came into the World also in 1920 while F.W. Murnau made Nosferatu a Symphony of Horror in 1922 plus The Last Laugh in 1924.
The term expressionism applied to music probably for the first time in 1918 focusing on Arnold Schoenberg. Members of the Second Viennese School included Anton Webern and Alban Berg alongside Schoenberg himself who avoided traditional forms of beauty to convey powerful feelings through dissonance.
Adolf Hitler rose to power in Germany during the 1930s causing Expressionism to decline there. The Munich exhibition Entartete Kunst occurred in 1937 marking a drastic shift in American reception where Expressionist works began increasingly acquired by American museums after this event.