An iamb has the rhythm "de-dum".
A couplet is a couple of lines that rhyme.
As an example of an iambic quadrametric couplet ("de-dum" four times in each line) - from Ogden Nash... Beneath this slab John Brown is stowed.
He watched the ads and not the road.
Yes
Shakespearian Sonnent
Simply put... A heroic couplet is two lines of rhymed iambic pentameter, while a couplet may still rhyme, but is not in iambic pentameter. The difference is the meter.
Sonnet.
During the mid-eighteenth century, the most popular type of poem was the heroic couplet. These poems consisted of rhymed pairs of iambic pentameter lines and were often used to express ideas with wit and elegance. Influential poets of this period, such as Alexander Pope, John Dryden, and Jonathan Swift, were known for their mastery of the heroic couplet form.
A couplet in poetry is a pair of consecutive lines that rhyme with each other. Typically, a couplet presents a complete thought or idea within those two lines. Couplet is a common form used in various poetic traditions.
English sonnet
iambic tetrameter
Badass ---- iambic tetrameter couplet
The most popular type of poem during the eighteenth century neoclassical era was the heroic couplet. This form consists of rhymed pairs of iambic pentameter lines, and was favored for its structured and formal style that reflected the values of order, reason, and restraint of the neoclassical period. Leading poets like Alexander Pope and John Dryden were known for their masterful use of the heroic couplet.
Unrhymed iambic pentameter
Any kind of rhyming couplet ends Shakespearean, doesn't have to be heroic The Shakespearean (or "English" or "Elizabethan") sonnet ends with a heroic couplet.