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Hi Steve, This appears to be schema used to help search engines understand the nature of content in objects containing "stuff" that search engines have trouble completely understanding. For example, I found keywords as possible markup element for a Video: http://schema.org/VideoObject I don't think this plays into rankings at all. Google is so over that kind of easy manipulation. However, I DO think that when these are marked up in conjunction with ALT attributes for images, or transcriptions for videos, they can help Google understand the semantic relevance of that content. For example (and I am totally making this up), imagine a video of a veterinarian administering vaccines to an animal. During the video the vet keeps referring to the animal as "the patient." So from the transcript, a search engine (or someone who's visually impaired) wouldn't know that this video is about medicine for animals instead of humans. Using the schema.org markup for keywords would allow terms like "animal vaccine best practices" to be included to help search engines understand better what the content is really about. That's my 2 cents. Hope it helps! Dana