A limerick is a short and silly poem that has five lines. The first two lines rhyme with each other, the third and fourth rhyme with each other, and the last line rhymes with the first two.
Limericks usually start with "There once was a..." and are often funny or silly. They can be about anything, like animals, people, or places.
Here's an example:
There once was a cat who could talk
He'd chat and chat when he'd go for a walk
People stopped to stare
But he didn't care
This cool cat was born to rock!
So, to sum it up, a limerick is a short and silly poem with five lines and a specific rhyme scheme. It's meant to make you laugh or smile with its fun words and silly story.