Okay kiddo, have you ever heard of the Prime Minister of England? They are like the boss of the country. Well, 10 Downing Street is the home and office of the Prime Minister. It's a fancy old building in London, England that has been around for a really long time. People know it as "Number 10" or "Downing Street" because that's the address - 10 Downing Street. It's a very important place where the Prime Minister makes important decisions about the country and meets with other important people. It's always guarded by big, tough-looking guards too!