There are lots of different events, some where sailors are in boats on their own and others where they are in small teams.
Courses are marked in the sea by a series of buoys, and competitors must be aware of their opponents and the conditions they will be sailing in.
What are the sailing classes?
49er - small boat crewed by two who have to leap about a lot. Has big sails and can go very quickly.
470 - crewed by a male and female sailor who at times have to lean way off the boat to take it where they want it to go.
Europe - a small boat that is sailed by women at the Olympics. One sailor per boat, who has to move around a lot.
Finn - a very tough boat to sail, by a single sailor. Some of the fittest sailors at the Games will be in this class.
Laser - a little boat, and every one in the fleet is supposed to be identical to all the others. An excellent test of sailing ability above everything else.
Mistral - the only windsurfing class in the Games. A huge physical challenge.
Star - crewed by two, one of the toughest boats to sail, many of the world's top sailors have competed in it.
Tornado - a catamaran and the quickest boat in the Olympics. Crewed by two, will be one of the most exciting events to watch.
Yngling - making its debut at the Olympics, is sailed by three female crew.
Sonar - three-person keelboat that is used in the Paralympics and the Olympics.
2.4mr - a small, heavy boat that is often used by disabled sailors.