Definition: There are four different running events. You would run for 1 stade, which is equal to 192 meters. 1 stade was one stadium.
This is the stadium. It is 192 meters -> one stade.
Rules: You would start at the beginning of the stadium. Then you would begin to run. Whoever crossed the finish line first won. The races ran from 1 stade (192m) to 24 stades (4,608m).
Fun Fact: There was one race where racers would run 2-4 stades in armor. This is probably the hardest running race in their Olympics.
This is the race that they ran in armor.
How is it Similar to Today?: Almost everything the Greeks did was the same to what we do today. We run in miles (meters for the rest of the world) instead of stades. They also run for longer distances. We don't run in armor today.