Medals are awarded when you complete a walk. The medal awarded depends on the length of the walk you complete:
Bronze Medal: Walks less than or equal to 399 kilometers (less than 582,000 steps approximately)
Silver Medal: Walks greater than or equal to 400 kilometers and less than or equal to 1,999 kilometers (more than 582,000 and less than 2,915,260 steps approximately)
Gold Medal: Walks greater than or equal to 2,000 kilometers (more than 2,915,260 steps approximately).