WCM tip #34: URLs between catalog items are rewritten to work correctly across all publishing channels
SharePoint 2013 introduces the cross-site content publishing model, where one or more catalogs located somewhere in your environment can be published on one or more websites. Because the catalog is decoupled from where it’s published, you can manage the content centrally and reuse it across multiple publishing channels.
One of the common challenges when working with centrally managed and reused content is creating links between the different items. Hyperlinks are path-based but when editing the contents of the catalog you don’t know how those contents will be published and what the exact location of the particular content items will be. SharePoint 2013 solves this issue by automatically rewriting links between catalog items. All links are replaced with a link to the catalog.aspx system page including the original path to the catalog item. Using search, SharePoint 2013 finds the catalog item and its URL in the particular publishing channel and automatically redirects to that URL using a 301 permanently moved redirect so that even Internet search engines can crawl the links between catalog items correctly.