Technically, the portion of the web that search engines like Google (GOOG) and Microsoft (MSFT) Bing catalog is called the “surface web” (though most people will think you’re a weirdo if you call it that). Less accessible portions go by other names.

For those who care to draw a distinction, the “deep web” refers to the region outside public view. This includes pages not indexed by standard search engines, such as password-protected sites, or ones tucked behind a paywall. Many people spend just as much time on the deep web as they do on the surface, if not more.

For example, your online bank account, your Netflix (NFLX) subscription, and perhaps your Facebook (FB) profile page are on the deep web. You’re likely well acquainted with this more private digital world—even if you didn’t realize it.

Finally, there’s the “dark web,” a mere sliver of the deep web. (Don’t worry; I’m not going to show you a diagram of an iceberg.)

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The dark web consists of encrypted networks that have been intentionally hidden from view, and they require special software to access them. Usually, when people refer to the dark web, they’re referring to content hosted on the Tor network, a system of relays that obscures IP addresses, or the locations of devices on a network. (Freenet and I2P are two other networks that support the dark web, but we’ll stick to Tor here.)

You can visit the Tor part of the dark web simply by downloading special browser software from the Tor Project’s website, and connecting to a URL that bears the top-level domain “’dot’ onion.” For instance, the Hidden Wiki, which is only accessible via the Tor browser, has a list of dark web sites. Be careful where you click though, as some sites may contain questionable—possibly even illegal—content.

While there’s no doubt plenty of shady stuff happening on the dark web, the network has a positive side. It helps political dissidents and whistleblowers escape surveillance and disseminate their views, for instance. Indeed, Tor was originally developed by the U.S. military in order to help route intelligence communications—and the U.S. government remains a major funder of the non-profit organization that now maintains it.

Sure, the dark web gets a bad rap for its association with criminal enterprises, like the Silk Road, a much maligned drug marketplace that operated for two years before the Feds shut it down in 2013. But some dark web users simply prefer the anonymity afforded by an encrypted network.

It’s not illegal to try to protect your privacy, after all.