Couplet

Def:
A couplet is a pair of lines(two lines that rhyme and have the same meter) of meter in poetry. Though not all couplets are rhyme. 
Examples:

True wit is nature to advantage dress'd;

What oft was thought, but ne'er so well express'd.

— Alexander Pope

 

Whether or not we find what we are seeking

is idle, biologically speaking.

— Edna St. Vincent Millay (at the end of a sonnet)

 

 

 

Sign:

Because there's more rhyme a couplets so it caught more attention in a poems, authors usually use couplets to emphasize the point.