I have found the function which outputs the category description:
function category_description( $category = 0 )
Now i need to locate the page, where all categoryes are populated, but it seems that I’m not able to find it (its not archives.php).
This tutorial states that archives.php is the correct file, but it seems like there has been some structure changed recently. Category.php is only the function holder, not populater.
WordPress 3.2.1
Solved the problem, it was just badly/non-conventionally built theme called LightWood and all the switching (pages, categoryes, archives) was done in index.php