Tor is a network for anonymizing connection data while you use the internet. It became popular because it is used by journalists to protect their privacy in countries with political censorship. Tor can be used for surfing, instant messaging, ssh, E-Mail and other things. Before you use this technique, I recomanded you to inform about the the basic concepts, the pro and cons (Using Tor will definetely slow down the transfer rate of your internet connection). This Wikipedia article is probably a good help.
The article describes how to install Tor for Ubuntu 10.04 using the Ubuntu and Tor Repositories. To get it working the installation of Tor itself is not enough; Tor needs extra settings!