What does peer guardian do and how does it work? There are anonymizing
proxies, there are incognito browser modes - how does peer guardian differ?

PeerBlock (formerly PeerGuardian) does not hide your address. PeerBlock is a
gate keeper that prevents IP usage on your PC. PeerBlock blocks incoming and
outgoing connections to Internet IP addresses that are included on blocklists
accessible over the Internet. What you are refering too is anonymous surfing, a
totally different subject. Please clarify what your objective is.

Look into Tor at https://www.torproject.org/ and follow the download links to
Linux, and specifically to Ubuntu. You are advised not to use the repository
universe for Tor packages which require you to edit as root the
/etc/apt/sources.list file to incorporate the repository at the Tor project -
see https://www.torproject.org/docs/debian.html.en for that information.
Otherwise, see: https://www.torproject.org/docs/tor-doc-unix.html.en , and read
the Tor documentation at https://www.torproject.org/documentation.html.en