The concept of deep web is easy. The deep web is that part of the network containing material, information and web pages that are not indexed in any of the existing search engines such as bing, google, yahoo, etc...
But this is impossible since many of the pages and documents are made in such a way that can not be indexable, either because they are password protected, why are made not indexable formats such as pages made entirely in flash, without content html, etc..
How Great is THE Deep Web?
Many of We will be surprised to know that the deep web has much more content than the surface web that we can access.
According to the Wikipedia in 2000 had the internet surface 167 Terabytes in size while the deep web had an 7500 Terabytes size which means that deep web content was 45 times the information we had access time.
All there in the deep web can not say that is inherently wrong. We can find interesting and diverse content such as:
1- Content stored by the governments of various countries.
2- Organizations that store information. For example NASA stores information about scientific research done. Other information can be stored weather data, financial data, directories with people, etc..
3- Crowd database of various kinds. The databases represent a very significant of the information stored in the deep web.
4- Forums variety of topics.
However we can also find very unpleasant content such as the following:
1- Selling drugs.
2- Pornography.
3- Black market thugs.
4- Pages to buy or make weapons.
Notably, 90% of content that exists in the deep web is accessible to all users.
If you want more information on what is available in the Deep Web, Down here there will be a link.http://www.youtube.com/watch?v=8eKjYUY7yqQ