What's to understand?

People put on silly costumes and bells and jump up and down waving sticks.

Naturally, the onlookers point at them, and laugh and call them nasty names, and pelt them with rotten vegetables and dead cats.

They get mad, chase the onlookers, waving the sticks, until the police grab them and lock them up as dangerous lunatics.

Then everything's peaceful until they're let out and it starts all over again.

P.