How does the banjo produce sound?

A banjo produces sound from string vibration. The strings rest on a wooden bridge, which is sitting on top of a banjo head, basically the same as a drum head you would find on a snare drum for instance, but special heads are made just for the banjo. When a string is plucked, the vibration travels from the string, to the bridge, then it is transmitted to the head of the banjo, so just like an acoustic guitar, no electronic amplification is needed.