The templating system was introduced in version 0.9.12, the choice was made to use Flat-Frog (previously known as Smarty-Light) which does basically uses the same syntax as Smarty but with much less functions, making it *lighter* (thus the previous name).
You don't need special knowledge (besides HTML/CSS) in order to take advantage of the templates, just open one of them and with the help of the inline comments, you should get the expected result(s) pretty quickly.
For those who are not familiar with the concept of templates, it's basically called by the main program (index.php) at the final phase (display), it will load the template, replace every content that need to be replaced and output HTML.
There is for now (release 0.9.12) 4 differents templates:
browse.tpl- Used when browsing directories
display.tpl- Used when viewing pictures (eith lowres or highres)
top-and-last.tpl- Used for lastcommented/lastadded and toprated pictures pages
navbar.tpl- Navigation bar (used in all templates)
If you want to customize the templates, please start by creating a new theme.