The page which linked to the current page.
When marketers speak of the Referrer, they mean the page which linked to the page currently being viewed by a visitor.
e.g. a visitor first searches for the term "cat food" on Yahoo!
They click on the first result, which is:
Therefore, the "Referrer" on the Wikipedia page is:
(e.g. the previous page which linked to it.)
The referring page is quite useful as it allows a marketer to determine:
The main problem with depending on the Referrer of a page to determine the source of your traffic is that many Web Browsers, Firewalls, Proxy servers, Virus Software, and Web Browser Plug-ins will block referrers from being sent to your site.
That means that a savvy marketer should not depend on the referrer being present to determine the source of traffic.