Originaly a drum machine. Used in the Hip-Hop/Rap culture.
Now known as making beats with your mouth.
In 1985 an MC named Doug E. Fresh introduced to the world the first human Beat Box. He did a song called "La Di Da Di" where he made the beat with is mouth and MC Ricky D (later known as Slick Rick) did ryhmes over it. The song became classic and people even tried to beat box as good as him.
There hasn't really been a good beat boxer than Doug E. Fresh, but nowadays theres another beat boxer named Rahzel that likes to copy song with beat box and make them as sound as close as possible. He is very excellent at human beat boxing and human turntablism
There a song called "Flash is on the Beat Box" by Grandmaster Flash which he uses a beat box, meaning a drum machine.