Im confused about the athletics competitions in the olympics?

Question

do those who run stints have to do more than one of these competitions or only one? for instance running a marathon? thanks

wikipedia lists these as the athletics: skim, dont read. get the idea

Track events

The track portion of Athletics will include, as it has in the past, sprints (100 m, 200 m, 400 m), middle-distance (800 m and 1500 m) and long-distance (5000 m and 10,000 m) events. Obstacle events will include hurdling (100 m and 400 m for women, 110 m and 400 m for men), relays (4×100 m and 4×400 m) and the 3000 m steeplechase.

Field events

The field portion will include the long jump, triple jump, high jump, pole vault, discus, shot put, javelin, and hammer throw for both men and women.

Combined events

Combined events will include the decathlon for men and the heptathlon for women. Each competition takes place over two days. The heptathlon combines 100 m hurdles, high jump, shot put, 200 m, long jump, javelin and 800 m. The decathlon combines 100 m, long jump, shot put, high jump, 400 m, 110 m hurdles, discus, pole vault, javelin, and 1500 m.

Road events

The road portion of Athletics will include a marathon and a 20 km race walk for both men and women. In addition, the men compete in a 50 km race walk.

Answer 1

They can compete in only one event.  Most only qualify in one event, like only the 100m or only long jump.  The top athletes can qualify in 2-3 events plus relays.

Answer 2

An athlete may compete in any number of events provided they do not clash in the time table. For example a track or field event may take place while the marathon is happening, making participation in both impossible.

Many athletes compete in several events, provided they are similar. For example, the great Carl Lewis ran in sprint races and did the long jump, but clearly being a good sprinter is an advantage for a long jumper. Kelly Holmes ran the 800 and 1500m. Many marathon runners made the step up from 10000m.

Heptathletes and decathletes tend not to participate in individual events for good reason. They won't even come close to winning any of the individual events, not even making the finals.