Heroic couplet is a form of iambic pentameter. They are a pair of iambic pentameters with a rhyming metric template such as aa, bb, cc and such.
Things base and vile, folding no quantity,
Love can transpose to form and dignity:
Love looks not with the eyes, but with the mind;
And therefore is wing'd Cupid painted blind:
Nor hath Love's mind of any judgement taste;
Wings and no eyes figure unheedy haste:
[…]
But herein mean I to enrich my pain,
To have his sight thither and back again (I.i.232-51)This speech by Helena in Shakespeare's A Midsummer Night's Dream has a series of heroic couplets of the rhyming pattern aa, bb, cc, and so on.
The fourteenth century English poet Geoffrey Chaucer, regarded as the father of English literature, is the first known to have used heroic couplet.
But wherfor that I spak, to give credence
To olde stories, and doon hem reverence, (The Prologe of Good
Wimmen, 97-98)This is an example of a heroic couplet from Chaucer's The Legend of Good Women.
The heroic couplet was further popularised by the seventeenth and eighteenth century poets John Dryden and Alexander Pope.