So how are IMPs and Match Points different?
IMPs are International Match Points and are a way of scoring Team Games where 4 to 6 players compete against another team. All international competitions are scored this way and work so well that they have been adopted for all club and tournament scoring. IMP or team games are very much like rubber bridge as the total score (above and below the line) is what matters. This score is compared to the opposing team who play the same hands. MPs or Match Points are used for scoring in duplicate games where it is not the total score you make on a hand but how well you do against all the other players who have the same hand. In match point play making 7NT on a hand can give you the same MPs as making 2 spades on another.
Bob Hamman, a world champion, puts it this way: What is the difference between IMPs and Matchpoints? Who do you think were the two best heavyweights who ever fought? I don’t really care who you pick, but take those two fighters, both at the peak of their careers, put them in a ring and let them slug it out for 15 rounds. Whoever wins is the champ. That’s IMPs. Now take the same two fighters, blindfold them and tie one hand behind their backs. Divide the ring diagonally with a solid barrier and put a heavyweight on each side of the barrier. Now go down to the local tavern and collect 20 drunks. Place 10 drunks on each side of the ring and let the fighters go at it. Whoever knocks out his drunks first is the winner. That’s matchpoints!— Bob Hamman, in Classic Bridge Quotes by Jared Johnson