allow your plugin to ‘hook into’ the rest of WordPress; that is, to call functions in your plugin at specific times, and thereby set your plugin in motion.
wp.org repo “Paste the following code to your Wordpress Theme file” “and you can copy one (and paste it to a theme file)” “paste this php code < ? php do_shortcode("[XX_123_123]"); ? > in any template” “Yes, you needed to edit your theme file for adding this function” WHY? Because the plugin author had no hook to count on in the theme