What is a referring URL?

I was under the impression that a referring URL was the blog who visited your blog? Is that not what it is? I'm new to this, any help is appreciated.
It's the url from which the visitor clicked a link to your page. It can be a url on your website or on a different site.
When a user clicks on a link in a web page, the user's browser moves to the specified link. When the browser requests the new page, it sends along the URL of the previous page. This "sent along" URL is called a referring URL