A limerick is a silly poem with five lines. They are often funny or nonsensical. Limericks were made famous by Edward Lear, a famous author who wrote the "Book of Nonsense" in the 1800's. This was an entire book of silly limericks.
How to write a limerick:
The first, second and fifth lines rhyme with each other and
have the same number of syllables (typically 8 or 9).
The third and fourth lines rhyme with each other and have the same number of syllables (typically 5 or 6)
Limericks often start with the line "There once was a..." or "There was a..."
Example of an 8,8,5,5,8 syllable limerick:
by Kaitlyn Guenther
There once was a wonderful star
Who thought she would go very far
Until she fell down
And looked like a clown
She knew she would never go far.
Kaitlyn was 12 or 13 when she wrote these, so the syllables might be a bit off, but they're close.