From Joomla! Documentation
Help with Joomla! 2.5
For help with a specific page within Joomla you can click on the help toolbar icon for further information about that specific page.
If you have only recently starting working with Joomla you will probably have experienced the pain of learning a new system. New terminology, new ways of doing things, perhaps even the web itself may be new to you. Then let this guide relieve some of that pain.
Further information about Joomla! 2.5
Joomla! 2.5 is the current version of Joomla but is only a minor upgrade from Joomla 1.7. Consequently, most of the resources that describe Joomla 1.6 and 1.7 will also apply to Joomla 2.5. Here is a selection that will help you get started.
For more information see the Joomla 2.5 category page.