To link to an external web page (not in Sitecore), use the Hyperlink Manager. Best practices when writing for the web dictates that links should never say "Read More." Instead, links should be written ...

There are two types of links: Internal Sitecore links and external hyperlinks. Internal Sitecore links are used when linking to other Sitecore pages or to files hosted on Sitecore's Media Library.

Facebook posts normally link you to another friend's page. These are still within the Facebook domain and are internal to that website. External hyperlinks are links that take you to another website.