Phonographs are, simply, devices that are able to both record and play back sound.
The first phonograph was invented by Thomas Edison in 1877. It was mass produced and marketed ten years later with minor changes.
Early phonographs transcribed sound patterns onto a cylinder, while later versions did so on a record disc. Once transcribed, the machines read the pattern and recreated the sound.
Phonographs are composed of a few major parts. The turntable is where records are placed, the stylus reads the record or the cylinder (in older models) and the amplifier creates the sound.
The phonograph made it so people could listen to music in the privacy of their own homes, without needing a live band nearby.