They're relying on us thinking it's about something. It isn't. There's absolutely nothing to understand. A person guesses how much money is in a box. No skill whatsoever involved. That's it. The entertainment comes from the possibility that the contestant may end up with a choice between two boxes, one containing 10p and the other �250,000 - but there's still no skill.
You pick a box, then start picking numbers of other boxes, the person opens the box and then that amount of money goes away. The idea is to be left with big numbers so the banker gives you a good deal, you can swap boxes at the end if the banker lets you. If you get to the end without dealing, you get whats in your box, unless you have swapped. It's all luck anyway. Beating the banker means you deal at aa price higher than that of the price in your box.