A Link Action is a workhorse. It points to any URL, including a website, blog, survey, app, or generally anything on the web. It's common to have multiple Link Actions on a page.
After selecting the Link Action, paste the destination URL in the URL box. The "Fetch" button will retrieve and populate the Preview metadata is available. You can edit it once retrieved.
Reference the Action Formatting and Controls FAQ for a refresher on the controsl that are common to Actions.