Runs another module's template function only if that module is active. If the module is missing or off, it shows nothing, instead of an error.
{jrCore_module_function function="jrRating_form" type="star" module="jrAudio" index="1" item_id=$item._item_id current=$item.audio_rating_1_average_count|default:0 votes=$item.audio_rating_1_number|default:0}{jrRating_form ...} would do the same, but breaks the page on a site without Item Ratings. Skin designers can't know which modules a site has, so use jrCore_module_function for functions from optional modules.