A DOI is a digital object identifier. It is a unique series of characters used to identify electronic objects such as publications and videos. You may notice that a paper you have published has a DOI. For open access papers that are deposited in PubMed Central, this DOI can be used to fetch your paper if you want to synchronize it with a video.
SciVee also assigns DOIs to videos and videos synchronized with media so they can be cited and easily found. If you synchronize a paper with a video, the paper DOI will be completely independent from the SciVee DOI.