Arrow's impossibility theorem

Arrow's Impossibility Theorem is a little bit like a game. It says that it's impossible for all of us to always be happy with the outcome, no matter how we play the game. Let's say three people want to decide which city to visit for their vacation. One person likes the beach, one person likes the mountains and one person likes the city. No matter how the three people decide who gets to pick what city to visit, someone won't be happy. The person who likes mountains won't get to pick if the other two people always agree, and the people who like the beach and city won't get to pick if the person who likes mountains always picks their favorite. So, it's impossible for everyone to always be happy, no matter what they decide.