Precise Pangolin is the codename for the Ubuntu 12.04 LTS release, which was published in April 2012 and will be supported until April 2017.
Lucid Lynx is the codename for the Ubuntu 10.04 LTS release, which was published in April 2010 and was supported on the desktop until May 2013 (already out of support) and on the server will be supported until April 2015.
More details about the different Ubuntu releases, their codenames, and support schedules can be found on the wiki:
https://wiki.ubuntu.com/Releases