While is a way of looping through lots of commands until the condition is fulfilled.
It is very easy to write bad while loops that never end.

While used in a times tables generator
This would output as
While used in CVC word generator
Some of the output might look like this
After pod appeared the user clicked 1 and it was appended to the list.
After fuw the user clicked 3 and the program printed the real_words list and then stopped when it reached the while command.