Limerick's are one of the most famous forms of poetry that have simple rules like
must have 5 lines
lines 1,2,5 rhyme
lines 3,4 rhyme
they will have a distinctive rhythm
they are usually funny
There was a young fellow named Hall
Who fell in the spring in the fall.
‘Twould have been a sad thing
Had he died in the spring,
But he didn’t—he died in the fall.