No other details were mentioned, but come on, it's UNO. What else needs to be said? You try to get rid of all your cards before everyone else, either by matching the color or number of the last card played. When you're down to one card, you have to say "UNO."

Occasionally, someone will be a huge jerk and play a "Draw Four" wild card, widely regarded as the biggest dick move in the game, but hey, do you want to win or not?