A World Record is the best performance in a certain discipline, usually a sports event.
In a number of sports, such as athletics or swimming World Records are set in a number of events that is regularly competed in over the world. The governing body of the sport is charged with recognising the World Records. In order for a record to be recognised, the event has to be held according to specific rules, and the athlete(s) in question usually have to be subject to a doping test.
The breaking of an existing World Record is often a big achievement in an athlete's career, and many athletes are still known because they set a new World Record, even if it was their only major achievement.
Not all events have World Records, as the achievements in some events are too dependent on the layout of the course or venue, which are not bounded by rules. Other events still keep records, but they are not regarded as significantly - for instance, marathon world records are regarded as far less important than on-track athletic events.
Outside sports, World Records can also be set in virtually anything that is measurable, but verifying these records is often difficult. The Guinness Book of Records collects and tries to verify all kind of World Records, from the fastest animal to the largest cheese ever produced.
