Surely all of you have heard fulfilled limericks - funny funny songs, often satirical content. Get their bums and lieberam, Dereham and deceivers. There are couplets humorous, humorous.
The word rhyme comes from "frequent", that is fast. Couplets (in some places they are called chants, it is hardly necessary to explain why) originated in Russia in the late 60-ies of the last century. It's a fast song in a clear rhythm dicotyledonous dance. The melody they have a very short - just a small verse so many times repeated with different texts.
A special type ditties - the so-called "suffering". They are more slow, melodious and lyrical content.
Couplets are often used in his works of Soviet composers. So, R. K. Shchedrin introduced ditty in his piano Concerto, the important role she plays in his Opera "Not only love".