The object of the game is to shoot the ball into the opponent's goal. The team scoring the most goals wins.

There are 10 players on each lacrosse team. Four of the players (a goalkeeper and 3 defensemen) must stay on the defensive half of the field, three (attackmen) must stay on the offensive half, and three (midfielders) can go anywhere on the field.  
Boys Lacrosse

The game starts with a face-off between two players on each team. The ball sits on the ground between the two players and the referee blows the whistle. This signals that the players can both try to get the ball.  Center face-offs are also used after a goal and at the start of each quarter.

The circular area around the goal called a crease. An opponent is not allowed to enter the crease, but they can reach in with their stick to pick up the ball.

A player may gain possession of the ball by dislodging it from an opponent's crosse with a stick check, which includes the controlled poking and slapping of the stick and gloved hands of the player in possession of the ball.

Body checking is permitted if the opponent has the ball. However, all contact must occur from the front or side, above the waist and below the shoulders. An opponent's crosse may also be stick checked if it is within five yards of a loose ball or ball in the air.

Fouls carry timed penalties, whereby the fouling player must be removed from play for a designated period of time without substitution.  Lacrosse personal fouls include tripping, unnecessary roughness, cross checking (making contact with another player with the stick between your hands), slashing (a stick check not on the opponents gloves or stick), or illegal body checking.  Like basketball, at 5 personal fouls the player is removed from the game.  Personal fouls may range from 1:00 to 3:00.

Some Lacrosse technical fouls include holding, offsides (not the right number of players on each half of the field), setting screens, stalling, and pushing.

If the ball or a player in possession of the ball goes out of bounds, the other team is awarded possession of the ball. If the ball goes out of bounds after a missed shot on goal, the player nearest to the ball when and where it goes out of bounds is awarded possession.

Advancement Rule.  Upon the start of any possession, particularly on a team's defensive end, the team must advance the ball into its offensive box area of the field within :10.