Pier is a CMS, it started as Smallwiki, then Smallwiki2, followed by Pier. Pier offers many features and functionality. The official site is http://www.piercms.com/, however it is somewhat dated. A better way to get started is download the latest image and install Pharo (using Version 331 of Pier and Pharo 4 as of 2015-May).
After having a running Pier image, one may need to upgrade (I've been running an internal wiki for Amdocs since 2005).