The deep Web refers to:

a$.$

websites that advocate violence toward people of a specific race, ethnicity, or religion.

b$.$

peer$-$to$-$peer file sharing networks that are used to illegally share copyrighted material.

c$.$

networks that allow only mutually trusted peers to participate in file$-$sharing activities.

d$.$

sites that cannot be indexed by Google and other search engines.

e$.$

seemingly innocent websites, containing malware that infects computers.