2M = 2-meter (also called Center-Forward)
These are players responsible for running the offense. Generally, 2-meters are big, athletic players with great leg support, good swimming ability, and poise. 2-meters need to be able to get & hold position, attack the goal with the ball, absorb fouls, pick the ball up quickly, and pass accurately. Defensively, 2-meters should match-up with the opposing team's drivers or 2-meter defenders and not get kicked out needlessly.

2MD = 2-meter defender (also called Center-Back)
These are players responsible for defending against the opposing team's 2-meters. Generally, 2-meter defenders are tall players with good leg support, long arms, individual toughness, and good swimming ability. 2-meter defenders need to be able to guard both in front and behind, and foul without getting kicked out. Offensively, 2-meter defenders should be good perimeter shooters.

U = Utility
These are players who are skilled at both playing 2-meter and defending 2-meters.

D = Driver (also called Attacker) ?
These are players responsible for attacking the goal by driving. Generally, drivers are small players with good hands and the ability to start and change directions quickly. Drivers need to have lots of tenacity, never quitting in their efforts to get free of their defender, get the ball, and score. Defensively, drivers should match-up with the opposing team's drivers.

G = Goaltender
These are players responsible for running the defense. Generally, goalies are tall players with great leg support and quick hands. Goalies need to be able to black the ball, protect the ball, and throw outlet passes with pinpoint-accuracy.