Explain the pun “the chicken crossed the playground to get to the other slide”

Pun also called paronomasia, is a joke exploiting the different possible meanings of word or fact that there are words that sound alike but have different meanings.

The examples of pun are

The best way to communicate with a fish is to drop them a line.
He bought a donkey because he thought he might get a kick out of it.
In the winter my dog wears his coat, but in the summer he wears his coat and pants.
Time flies like an arrow. Fruit flies like a banana.
A chicken crossing the road is poultry in motion.
Energizer Bunny arrested -- charged with battery.
A skunk fell in the river and stank to the bottom.
The chicken crossed the playground to get to the other slide.
The best way to stop a charging bull is to take away his credit card.
The marine biology seminars weren't for entertainment, but were created for educational porpoises.
Why are fish so smart? Because they live in schools.
What do you get from a pampered cow? Spoiled milk.

The pun “the chicken crossed the playground to get to the other slide” is about the behavior of chicken which is funny, and in conversational way it is illustrates as follows