The matches are 18 hole match play, meaning if your team (say Woods/Strickers) get a 4 on a hole and their opponents (Rose/Poulter) get a 5. then Woods/Stricker would be 1 up in the match. Low score on the hole wins the hole for the team. They play 18 holes or however long it takes for one team to close out another team. So if Tiger/Stricker are 3 holes up with 2 holes to play, they won't play the last two holes because there would be no way Rose/Poulter could win the match.
When a team (USA or Europe) wins a match, their TEAM gets a full point.
When the two teams tie (Stricker/Woods vs. Rose/Poulter) are dead even after 18 holes, then the match is halved and each team gets a half point.
There are 28 total match over the weekend.
Europe needs 14 points to retain the cup, USA needs 14.5 points to win the cup.