In the old days, when there was no concert halls and music halls, instrumental music and a small vocal works were performed, mainly in the homes of music lovers. Gathered a few friends that are musicians, he put up the stand for music, panels, removed from casings and casings violins, violas, cellos, and sometimes flutes and oboes, someone sat at the harpsichord, and started home concert. Sounded sonatas, trios, quartets. Sometimes someone sang to the accompaniment of harpsichord or other tools. Students usually only a few people were relatives and friends.
Played this way, and in the modest houses of the artisans, and aristocratic salons. Hence it is the expression goes - chamber music (camera on-Italian - room), then there is music intended for performance in a large hall or in the Church, and in the room, the music home. It is clear that in the room it was impossible to play a Symphony, to sing Opera or oratorio. Therefore, the chamber called works, written for a small number of performers - solo instrumental pieces, duets, trios, quartets, songs and romances, which you can do at home.
And although chamber music came from living rooms to concert halls, the old name was retained. However, now they are trying to do in large concert halls, where usually sound symphonies and oratorios, and in the smaller chamber halls.