You can earn money from the relevant advertisements that run against the videos uploaded by you. The program is based on ‘Cost Per Impression’ advertisement concept. Google uses their advanced algorithms to find out the relevant keywords to ensure that the click rate is higher.
Looks like a familiar concept? Yes, it is the same concept that google uses for adsense. To be precise, Youtube Partner Program is like ‘Google Adsense for Videos’. All that you need to have is one or more video with quality content (do not use any obsessive content or racial discrimination content) and good number of visitors. Go to Youtube Partners page and apply for it. It is FREE to Apply and a chance to earn revenue based on the hits your videos get.