Live Themer watches for the use of certain theme hooks when rendering a page (eg block, page, comment etc). When Drupal's theme engine renders one of these, Live Themer stores the render array (or, if not available, the variables array sent to the theme_hook() function in question), so it can later regenerate the same theme hook but with a different *.tpl.php file or theme function.
* a serialised array containing template suggestion information and variables which are fed as necessary into templates via a preprocess function. The theme layer is given this array thereby not requiring the Livethemer Inspector module to be active whilst simply using the theme.
* a CSS file which is dynamically generated by the module. This CSS file can be aggregated using Drupal's usual method.