Download Joomla Templates

please hel me!!!!
i can work with php nd i can develop standard website using php,ajax,javascipt.do i need to learn JOOMLA.
if( needed)
{
Why???????;
give me some addresses of good joomla tutorial

}

http://www.siteground.com/tutorials/joomla/index.htm

http://www.joomlatutorials.com/

http://docs.joomla.org/Tutorial:Creating_a_basic_Joomla!_template

http://www.compassdesigns.net/tutorials/48-joomla-template-tutorial.html

http://www.netshinesoftware.com/joomla/joomla-tutorial.html

http://help.joomla.org/content/view/773/125/