There is a lot of confusion defining 5 levels of web : surface web, bergie web, deep web, charter web, marianas web. 5 levels of web are commonly percepted with a same level of uneducated fear as 7 gates of hell.
I found a very interesting and infographic defining 5 levels of web in simple terms.
5 levels of web, deep web
Quote from Endgadget:
Depending on where you get your Mariana’s Web myths, it’s where you’ll find “the darkest secrets humanity has in its history,” the secret location of Atlantis and “the Vatican secret archives,” or a database of archives belonging to the most powerful intelligence agencies on Earth. Many believe that Mariana’s is home to an all-powerful, female artificial intelligence entity.