From Joomla! Documentation

Hathor is a Joomla! administrator (back end) template included with the distribution of the Joomla! CMS starting with version 1.6. It is designed as a standards compliant interface that makes the Joomla! administration possible for all users including those with disabilities and using assistive technology.

Working with Hathor

Modifying the Hathor Color Scheme

Principles Behind the Hathor Layouts