IT’S TO EAT!!!! MAZEL TOV!
Well, that covers almost EVERY Jewish holiday. As Jackie Mason says, most Jewish Holidays are like this:
Shavuout is one of the few holidays where points one and two don't work. It's actually the giving of the 15 (er, 10! 10!) Commandments to the people of Israel.
Point 3, however, is still in play.