So let's say, if you can guess who the champion team is for soccer, such as in World Cup, then you win a car. Otherwise, you win a goat.
There are 4 teams left. Country A, B, C, and D.
And country A will play country B, to go into Final match. Country C will play country D, and go into Final match. Then in the Final match, the champion team will be known.
So you choose Country D. And now you go into a room and cannot watch TV, cannot use a mobile phone or Internet, and cannot communicate with the outside world at all.
Now Monty Hall sits in another room and watch TV for the match between country A and B. Now he finds that country A won the match.
Then he comes to you and the Monty Hall show continues. He said, "now, I can tell you Country B is not the champion team. Will you want to switch your choice?"
Just like Monty Hall opening a door and tells you it is not the car, now he tells you Country B is not the champion team. Will you switch your choice?
What if Monty Hall also watched the match between country C and D and tells you Country C also did not win. Will you switch?