Crossposting is the act of posting the same document to multiple venues. Crossposting content to different sites can be useful because different audiences respond differently to the same content.
It’s possible to just host the content on your website and drop a link for other sites, but keep in mind that people may be too lazy to click on a link if they don’t know why it might be relevant for them. Including a quote or copy-pasting the whole article may be better.