April Fools’ Day is called that because it’s the day when people play practical jokes, hoaxes, and harmless pranks on each other.

Why the name stuck

The “fools” part refers to the person who gets tricked, or sometimes the prankster if the joke is revealed by calling them an “April fool”.

Where it came from

Its exact origin is unclear, but one common explanation is that it developed as calendar systems changed in Europe, and people who kept celebrating New Year at the old date were mocked as “fools”. Other theories exist too, but historians generally agree the true origin is uncertain.

In practice

Today, it simply means April 1 is the annual day for jokes and pranks, usually meant to be lighthearted.

If you want, I can also give you a 1-sentence kid-friendly version.