There are some army generals who need to work together to attack a city, but they can only send messages to each other through a messenger. Some of the generals might be bad and send wrong messages, so they need a way to still work together and win even if that happens. It's like playing a game and some people might cheat, but they need to find a way to still play fairly and win.
This is the Byzantine Generals Problem
Bitcoin is the solution, the honest naked truth!