A video's proof page is a tool that lets you share and get feedback on your video content with others before publishing it to your webpage.
When uploading a video or editing the video details page of a video you will be asked if the video is a proof video. Simply answer yes to this question. Now that you have indicated that you would like access to the proof page of a video you will now see a 'Proof Page' link within the right hand menu of a video's details page. Simply click this link and review the video. One the proof page you can invite others to view the video, leave time based comments or comments about the video as a whole, and even upload an updated version of the video for further reviewal.