What is a Darknet?

Nowand then I see the term 'Darknet' online, and you've probably seen it,too.  So what is a Darknet? Well, itdepends on who you ask.
Thereare several terms bouncing around the Internet: Dark Web, Deep Web, Deep Net, and Darknet.  Oh, and Anonymous Networks.  It gets confusing.  This post will simply address Darknets and AnonymousNetworks, and save the remaining terms for another day.
Let'sstart with how the Internet normally works. You want to visit a website, so your computer sends a request in theform of data packets.  Each packet isaddressed with where it came from (your computer) and where it's going (thesite you want to visit).  When a datapacket reaches a web server, it looks at the address, and passes it along tothe next server until it reaches its destination. 
YourIP address, which is the key to your location and identity, remains knownbecause there is a clear trail from your computer to its destination.
In2002, four Microsoft employees wrote a paper titled, "The Darknet and theFuture of Content Distribution." Their angle was that protecting copyrighted material like music with DRM(Digital Rights Management) would be difficult if people resorted to file sharingon their own private Darknets.
Darknetsare decentralized, non-commercial, private networks that function using P2P(peer to peer) or F2F (friend to friend) protocols. 
Whatdoes that mean? A Darknet is where people go to anonymously share files.
PopularTorrent-style sites that share music and games may not be true darknets becausethey are not between trusted peers, but instead let any user connect with anyother.
However,even Darknets are not truly anonymous because your Internet Service Providercan inspect your data packets if they think you're sending spam or piratinggames or something nefarious.  To counterthis, some users move to Anonymous Networks like Tor and i2p, which use 'onionrouting.'
Onionrouting places layers of encryption around your data packet, and as the packetmoves from router to router, a layer of encryption is peeled away.  By the time it reaches its destination, thatweb server can only see the last place the packet came from, not its originallocation (your computer).
Likeany technology, Darknets and Anonymous Networks can be used for good orevil.  Credit card thieves, childpornographers, and pirates can use them to sell or trade files.  However, citizens of oppressive regimes like Syria,Iran or China can use them to communicate and organize with less fear of beingarrested.
Ididn't find data on how many Darknets are in use or how many people use them,but I think they are here to stay. People want online anonymity for a variety of reasons, and that ismotivation enough to keep building new Darknets every day.
(I drew information fromWitnessThis (especially the Comments section), Null Byte and Wikipedia.  The pic is from:  Vagabondish)