Banjo is a stringed instrument of African-American origin, in the United States. It is an adaptation from the African Instruments of similar type. Though Banjo is associated with the Country and Folk Music Genre, it is used in Rock, Pop and Hip-Hop songs.
Banjo has a thin membrane stretched over a frame or cavity, which forms as a resonator. The membrane is usually of plastic and animal skin can also be used. Modern Banjos come in four, five and six string versions. Sound is produced by plucking the strings by fingers.
The body of Banjo is usually made of wood and of circular shape. A thin membrane is stretched over the open end of the pot shaped body and tensioned similar to a drum head. There are Frets on the long arm in the modern Banjos. The fourth string is usually wound with either steel or bronze-phosphor alloy.
On some Banjos, you can find a separate resonator plate on the back of the pot. This is used to project the sound forward and thus giving more volume. There are Open-Back Banjos as well which have a mellow tone compared to the resonator Banjos and have different setup.
Here is a video on basic Banjo lesson.