There are two types of racing - fleet and match racing.
Fleet race: Numbers of competitors line up and race against each other.
Match race: Two competitors racing head to head, with slightly different racing rules that allow aggressive tactics.
At the 2012 Olympics Irish sailors are only participating in fleet racing.
There are a series of races over a few days and points are awarded in each race. first scores one point, second scores two points, etc.
After 10 races (15 races in the Skiff (49er) event), points from the worst race are discarded. The remaining points are added together.
The 10 best athletes/crews then advance to the medal race. Points are doubled, so first place gets two points, second gets four, etc. The points total after the medal race determines the placings. The athlete/crew with the lowest number of points is the winner.
For more information on the Sailing competition at London 2012 and the rules, go to the website of the International Sailing Federation (ISAF), the governing body for the sport.
Some useful terminology:
Helm - the helm is the tiller or wheel that directs the boat in different directions. Helm is often used to describe the person who drives the boat too
Aft - The back of a boat. If something is located aft, it is at the back of the sailboat. The aft is also known as the stern.
Bow - The front of the boat is called the bow. Knowing the location of the bow is important for defining two of the other most common sailing terms: port (left of the bow) and starboard (right of the bow).
Port - Port is always the left-hand side of the boat when you are facing the bow. Because "right" and "left" can become confusing sailing terms when used out in the open waters
Starboard - Starboard is always the right-hand side of the boat when you are facing the bow.
Leeward - Also known as lee, leeward is the direction opposite to the way the wind is currently blowing (windward).
Windward - The direction in which the wind is currently blowing. Windward is the opposite of leeward (the opposite direction of the wind).
Mast - the big pole that holds the sails up
Boom - The boom is the horizontal pole which extends from the bottom of the mast. Adjusting the boom towards the direction of the wind is how the sailboat is able to harness wind power in order to move forward or backwards.
Rudder - Located beneath the boat, the rudder is a flat piece of wood, fiberglass, that steers the boat. The rudder is connected to the helm.
Tacking - This basic sailing manoevre refers to turning the bow of the boat through the wind so that the wind changes from one side of the boat to the other side. The boom of a boat will always shift from one side to the other when performing a tack or a jibe.
Jibing - The opposite of tacking, this basic sailing manoevre refers to turning the stern of the boat through the wind so that the wind changes from one side of the boat to the other side. The boom of a boat will always shift from one side to the other when performing a tack or a jibe. Jibing is a less common technique than tacking, since it involves turning a boat directly into the wind.