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;

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.