Kulturforum actually is the name of the entire area, of which the Neue Nationalgalerie and the gold-coloured Philharmonik are also parts of. But the name Kulturforum is often (and now by me as well) used to refer to the Kunstgewerbemuseum, the Gemäldegalerie and the Kupferstichkabinett, which are connected with eachother through a huge building near Potsdamer Platz.
During the Cold War there was sufficient space to build, so close to the wall. It turned the Kulturforum into the modern centre of art in West Berlin. The halls sometimes also give host to exhibitions of contemporary artists such as photographer Mario Testino.