This Video Will Teach You 2 YouTube SEO Tips For Metadata and optimizing your metadata.
So for quick reference YouTube metadata is just a techie way to explain the titles, descriptions, tags, cards, thumbnails and captions of a You-Tube video.
Metadata can be added while you're uploading your videos, and you can also edit this information anytime afterward, however it is best to leave it once a video is ranked on the YouTube platform.