Tails is a live operating system that you can start on almost any computer from a DVD, USB stick, or SD card.
It aims at preserving your privacy and anonymity, and helps you to:
use the Internet anonymously and circumvent censorship;
all connections to the Internet are forced to go through the Tor network;
leave no trace on the computer you are using unless you ask it explicitly;
use state-of-the-art cryptographic tools to encrypt your files, emails and instant messaging.