Some couplet poems by famous poets include "One Happy Moment" by John Dryden, "Hero and Leander" by Christopher Marlowe and "An Essay on Criticism" by Alexander Pope. Shakespeare is also famous for using couplets in his sonnets.
A couplet is two rhyming lines. It can be used as a standalone short poem, or it can be used in a larger poem with other couplets or types of poetry. Lines in a couplet typically have the same meter.
If the two couplets contain a complete thought, it is called a closed couplet. It makes sense independently of the rest of the poem's context. If the couplet needs other lines to make a complete thought, it is an open couplet.
A famous Shakespearean couplet is a line from the play, "Hamlet." Hamlet says, "The time is out of joint. O cursed spite // that ever I was born to set it right!" In addition to rhyming, both lines mirror each other in number of syllables and meters. This is a traditional style of most couplets.
Couplets are not unique to English literature and poetry. They were used in ancient Latin poetry, and they are classically used in Arabic and Chinese literature as well.