Libraries contain books and other printed materials whereas Archives contain records.
Unlike books, which are written after the events they describe, archival records are created during the course of an event as part of a person's or organization's regular activity. For example, a student studying the Civil War might wish to read the letters written by a soldier during the war. Libraries are also generally considered collecting bodies, which means that they do not derive their materials from a particular institution but rather from anyone and anywhere. Archives, on the other hand, tend to be receiving institutions. Archives are generally established to preserve the archival materials produced by the organizations or institutions they serve.