Track cycling discipline - a middle-distance world championships and Olympic event for both men (50 km) and women (30 km).
The points race is a massed start event for as many riders as can be safely accommodated on the track. Placings are determined by points awarded for a series of sprints at regular intervals (usually every ten laps or 5 km or so); the usual scoring is 6,4,2 and 1 points for the first four riders with double points on the final sprint of the event. However, the points score is in fact only of secondary importance since riders who gain or lose a clear lap on the field are placed first by the lap they are on and only then by points. This opens up the tactics of the race; a rider may attempt to sneak a lap early on (when the race otherwise tends to be very stop-start) and then just police any subsequent breakaway attempts, while a rider who has been shut out of the points scoring may still have a chance to bid for glory in the closing laps. As the observant reader will have realised, the first rider across the finishing line at the end is not necessarily the winner.
A minor variant on the points race at minor track meetings is the course des primes where the intermediate sprints are for prize money rather than points towards a classification. The madison is also basically a points race variant.
Update 26 August 2002:
The UCI in their august wisdom have now seen fit to change the standard points race rules (as of the 2002 World Junior Championships) - riders lapping the field are now given 10 bonus points but the lap's advantage does not confer any further advantage. This effectively makes it advantageous for a lapping rider to hang just off the back of the field for as long as possible, thus maintaining their position as the front of the race and mopping up the points for as many of the subsequent sprints as they can, before completing the lapping process to claim the bonus points.