Sides and Matches
Side: A player, or two or more players who are partners.
Single: A match in which one plays against another.
Threesome: A match in which one plays against two, and each side plays one ball.
Foursome: A match in which two play against two, and each side plays one ball.
Three-Ball: A match play competition in which [...]

Observer
An “observer’’ is one who is appointed by the Committee to assist a referee to decide questions of fact and to report to him any breach of a Rule. An observer should not attend the flagstick, stand at or mark the position of the hole, or lift the ball or mark its position.
Obstructions
An “obstruction’’ is [...]

Hazards
A “hazard’’ is any bunker or water hazard.
Hole
The “hole’’ shall be 4¼ inches (108mm) in diameter and at least 4 inches (100mm) deep. If a lining is used, it shall be sunk at least 1 inch (25mm) below the putting green surface unless the nature of the soil makes it impracticable to do so; its [...]

Addressing the Ball
A player has “addressed the ball’’ when he has taken his stance and has also grounded his club, except that in a hazard a player has addressed the ball when he has taken his stance.

Advice
“Advice’’ is any counsel or suggestion which could influence a player in determining his play, the choice of a [...]