A silent film is a film with no synchronized recorded sound (and in particular, no audible dialogue). Though silent films convey narrative and emotion visually, various plot elements (such as a setting or era) or key lines of dialogue may, when necessary, be conveyed by the use of title cards.
The term “silent film” is something of a misnomer, as these films were almost always accompanied by live sounds. During the silent era that existed from the mid-1890s to the late 1920s, a pianist, theater organist—or even, in large cities, a small orchestra—would often play music to accompany the films. Pianists and organists would play either from sheet music, or improvisation. Sometimes a person would even narrate the intertitle cards for the audience. Though at the time the technology to synchronize sound with the film did not exist, music was seen as an essential part of the viewing experience. “Silent film” is typically used as a historical term to describe an era of cinema prior to the invention of synchronized sound, however it also naturally applies to sound-era films such as City Lights and The Artist which are accompanied by a music-only soundtrack in place of dialogue.
The term silent film is a retronym—a term created to retroactively distinguish something from later developments. Early sound films, starting with The Jazz Singer in 1927, were variously referred to as the “talkies”, “sound films”, or “talking pictures”. The idea of combining motion pictures with recorded sound is nearly as old as film itself, but because of the technical challenges involved, the introduction of synchronized dialogue became practical only in the late 1920s with the perfection of the Audion amplifier tube and the advent of the Vitaphone system. Within a decade, the widespread production of silent films for popular entertainment had ceased, and the industry had moved fully into the sound era, in which movies were accompanied by synchronized sound recordings of spoken dialogue, music and sound effects.
Most early motion pictures are considered lost because the nitrate film used in that era was extremely unstable and flammable. Additionally, many films were deliberately destroyed because they had negligible continuing financial value in this era. It has often been claimed that around 75 percent of silent films produced in the US have been lost, though these estimates may be inaccurate due to a lack of numerical data. (Wikipedia)