A friend asked me to explain UTXOs yesterday. So I said to him: "That's the same thing you get when someone gives you a million dollars. It's cool, but it's better to have the million in paper money, because if someone gives you a million dollars in change, there'll be enough to fill a truck. You'll spend the bigger bills a lot better and it'll definitely be cheaper than driving around with a truck full of change and shopping with it."
How would you explain UTXOs to someone who doesn't understand bitcoin at all?