This means that the poem consists of pairs of lines that rhyme with each other. The most common rhyme scheme is iambic pentameter, meaning that each line has ten syllables, with an alternating pattern of unstressed and stressed syllables.
Here is an example from the General Prologue:
"A-bout his char-acter, and all his life,
And every de-tail of his art and wife."
This type of rhyming helps to create a flowing, musical quality to the text, and it also helps to highlight the humor and satire within the tales.