Flag variables explained
Remember practicing multiplication tables as a kid and your teacher repeatedly asking you what "5 x 9" was until you got it right?
In this situation, the flag variable was whether or not you got the problem correct.
If you answered the problem incorrectly, the teacher would continue the loop of asking you the question.
However, if you answered the problem correctly, the teacher end the loop and stop asking you the question.
In other words...
A flag variable is a boolean value that signals to a while loop whether or not to continue running.
Coding a flag variable
Let's take the situation above and apply it in Python terms to get a better idea of how it works. I've coded the majority of the program, that way we can focus on how the flag variable works.