A silent movie is a movie made without sound. Silent movies were made from the late 1880s to the early 1930s. They used early cameras that could not record sound. Either the movie was being made before sound cameras were invented, or the movie makers could not afford the expensive new equipment.
Charlie Chaplin was known as one of the best movie stars during "The Silent Era", as it's called today in movie history. Some silent stars also did well in sound movies. Popular silent movies include Nosferatu: A Symphony of Terror, A Trip to the Moon, The General, and Metropolis.