Using it is easy-as-pie. First, plug the Ethernet cable into any Internet provider in your home, work, hotel or conference/event. Next, power up the Pi with the micro USB cable to your laptop or to the wall adapter. The Pi will boot up and create a new secure wireless access point called Onion Pi. Connecting to that access point will automatically route any web browsing from your computer through the anonymizing Tor network.
If you want to browse anonymously on a netbook, tablet, phone, or other mobile or console device that cannot run Tor and does not have an Ethernet connection. If you do not want to or cannot install Tor on your work laptop or loan computer. If you have a guest or friend who wants to use Tor but doesn't have the ability or time to run Tor on their computer, this gift will make the first step much easier.
Tor is an onion routing service - every internet packet goes through 3 layers of relays before going to your destination. This makes it much harder for the server you are accessing (or anyone snooping on your Internet use) to figure out who you are and where you are coming from. It is an excellent way to allow people who are blocked from accessing websites to get around those restritions.
According to the Tor website:
Journalists use Tor to communicate more safely with whistleblowers and dissidents. Non-governmental organizations (NGOs) use Tor to allow their workers to connect to their home website while they're in a foreign country, without notifying everybody nearby that they're working with that organization.
Groups such as Indymedia recommend Tor for safeguarding their members' online privacy and security. Activist groups like the Electronic Frontier Foundation (EFF) recommend Tor as a mechanism for maintaining civil liberties online. Corporations use Tor as a safe way to conduct competitive analysis, and to protect sensitive procurement patterns from eavesdroppers. They also use it to replace traditional VPNs, which reveal the exact amount and timing of communication. Which locations have employees working late? Which locations have employees consulting job-hunting websites? Which research divisions are communicating with the company's patent lawyers?
A branch of the U.S. Navy uses Tor for open source intelligence gathering, and one of its teams used Tor while deployed in the Middle East recently. Law enforcement uses Tor for visiting or surveilling web sites without leaving government IP addresses in their web logs, and for security during sting operations.