The Little (but not the littlest) Fugue in G Minor, by J. S. Bach

Just as rap, disco or a waltz can be recognized by its style or structure, so can a fugue if you know what to listen for.

In layman's terms, a fugue begins with a solo line which states the melody, usually in one of the hands.  Then the other hand comes in and imitates the same melody while the first hand goes off wandering by itself.  The two hands then come back together, they frolic a bit, then one of them may restate the melody.  The restatement is like a mating call because this usually attracts the attention of the feet who then enter into the fray.  Then the hands, like a tease, go scattering.  After the feet have their say, all the body parts play tag for a while until one of them states the theme one final time, usually the feet get this honor since they were the last in. 

Chorally, in this fugue, the voices enter first in the soprano, then the alto, the tenor, then the bass.   They continue: T, S, A, B, S, B.