Joomla 1.6 Overview
From Joomla! Documentation
What was Joomla 1.6?
Joomla 1.6 should no longer be used for production sites, with it recommended that users upgrade to Joomla 2.5 (which should be a seamless update in most cases) or updated to the currently supported version of Joomla.
See the Learn > More About Joomla! for more information about what Joomla can do.
Starting With Joomla
To get find out more about how to get stated with Joomla, go to Learn > Beginners