Marco Said: "Now you've mentioned repositories, but that's not a complete answer either. First, not all of FTM's templates use repositories. Second, a link to a repository is probably insufficient to help someone locate a particular record. In other words, a URL should, whenever appropriate, be included with a repository, source, citation, and citation media. This is not redundant. A repository points to a domain like familysearch.org. A source points to a particular record collection like a parish register, e.g., new.familysearh.org/parishregisterX. The citation will have a link to the particular record (or page) of that register, e.g., new.familysearch.org/parishregisterX/page52. All three of these will be different URLs. Only the citation and citation media will contain the same URL, but that is necessary for each to stand alone."

I agree with everything except the last point. The source_citation and source_citation.media probably will not point to the same place if the media is a picture representation of web page where you found the information at the time you collected the citation that you captured and saved to your hard drive. This way you can show users and yourself what you found years down the road when the site moves the data or the site goes away.