The Training Bar tells you how much you have trained your Tamagotchi. He or she will gain one (1) notch on the bar (up to 10 notches) whenever one of the following occurs:
>He or she is crying or in a bad mood and you praise them
>He or she beeps without needing anything and you give them a time out
>He or she gives a poop or snake to another Tamagotchi on purpose and you give them a time out
You can find more information on the Training Bar in the Tamagotchi manual regarding when to use the Discipline ("Pac-Man") Icon.