This is going to be tough to explain. I have created a custom theme and have a file called: categories.php, in this file i have:
<?php $args = array('hide_empty' => FALSE); wp_list_categories($args); ?>
This displays all my categories as links, even the ones without a post associated with them.
My permalink structure is this /%category%/%postname%/ so when i click a category name i go to http://example.com/category/action/. This is fine but what i'm struggling with is what file i have to create and what i have to put in said file so it displays all the posts from the clicked category?