Deep linking is the process of pointing a visitor to a specific page in a website through the use of that page’s link instead of that of the home page. When the user clicks on that link, he/she is taken directly to a page deeper into the website. This is useful for quickly and directly referencing a specific page or article among many, rather than just sending a user to the home page.
Techopedia explains Deep Linking
Deep linking is essentially just embedding or posting the direct link to a specific page of a website instead of its home page. An example of a deep link is http://www.example.com/specific_page, where "example.com" is the home page.
The Hypertext Transfer Protocol (HTTP), the technology behind the Internet, does not really distinguish between any links, deep or otherwise; they are all functionally equal. This is intentional in design since the purpose of the Web is to allow authors and content providers to link to any published document to any site.