A useful plugin for boost the website traffic is wordpress video locker wich is a simple video locker and if you want to play the video you need to share it on facebook, after share the video is reloaded and starts playing. If are asking how the traffic is made, just think about the people who sees the link that you have shared from that number of people a mall parts of them share your url and so on.
If you have a website where you post videos you should download wordpress video locker and see the results.