Greetings, The internet is generally categorized into the visible (surface) and invisible (deep) web. You're already familiar with the surface web, because it's what we use to browse every day. In order to understand the deep web, you need a basic understanding of what the internet is and what search engines do. The Internet The internet is a service that interconnects different computers and devices around the world. Essentially, it's a collection of networks that exist and are shared with each other around the globe. This means that every single device that connects to the internet is connected to some sort of network. There are billions of people on the planet - imagine if every single one of them connects to the internet and uploads a few files or share some files on a network? Naturally, there's a chance for some of the data to get lost, corrupted, secured, hidden, etc... Search Engines Search engines find websites based on several algorithms, crawlers, bots, etc... Essentially your website is found based on its content, it's SEO (search engine optimization), accessibility, among other factors. It can do this due to the fact that your web host gives knowledge of the existence of the website. Once the search engine is alerted, it'll scan your website with these algorithms to determine if it should get a ranking (displayed as a result) or if should get ignored. The Invisible Web The invisible web consists of those documents that are hidden from search engines. They can intentionally be made private, it can be lost data, unlinked pages, corrupted data, stolen data, etc... It's important to know that the Visible Web is much, much smaller than the Invisible web - however, the visible web contains the most relevant and important documents. It's not illegal to access the invisible web, but you should be very careful when doing so. It's littered with viruses, malware, adware and all sorts of software that can compromise you, your privacy and the general security of your PC. I hope this gives you a clearer understanding. Kind Regards, Hishido