If the Surface Web is the indexable part of the internet, the Deep Web is everything else. The Deep Web is the area on the internet that can't be, or isn't, indexed. And it's much, much bigger. This is because the Deep Web includes much more than what you probably think. Remember—the internet isn't the World Wide Web (Surface Web). It's the infrastructure over which the Surface Web is accessed. So, the Deep Web (most of it, anyway, but we'll talk about that soon), also exists on the internet. Any website or system that requires login credentials is part of the Deep Web.

Organizational information and intranets of businesses, academic institutes, governmental departments, and others, are also part of the Deep Web, as are websites that specifically prevent search engines from indexing parts of the website, such as Google Scholar, or Amazon.

The following screenshot displays searching for deep web in Google Scholar:

As you can see, there are results.

After clicking the Accessing the deep web link, note the following:

We arrive at a login screen. So, the article itself is on the Deep Web, but its title and metadata was indexed by Google, and therefore was returned as a search result.

Now, let's understand what we just read—the Deep Web is accessible using any standard browser, but is not indexed by search engines, so you usually need to either enter a username and password to access the content or be in a specific network (company or university network, for example).

But what about the Dark Web?