The internet has long been an essential fixture of people's lives. But the candy-colored cupcake photos on Instagram and hilarious animal videos on YouTube are just the sugar-coated, cat-tastic surface of the internet.

There's also the web's seamy underbelly — an anonymous hidden marketplace that serves as a hotbed of drug and arms trafficking, fraud, hacking and other cybercrimes.

The following are questions and answers on the so-called dark web, accessible just a few clicks away on any computer.