Collect cards into melds and have as little deadwood as possible at the end of a game.
Forming melds and eliminating deadwood.
A meld is a group of 3 or more cards
RUN =♥3♥4♥5 SET =♦8♥8♣8
You end up with 10 or fewer points of deadwood
You end up with no deadwood
If your opponent has less deadwood, they score the difference plus 25 bonus points.
If you go GIN without the need of discarding a card, you get 31 bonus instead of 25.