Hooks are a way for one piece of code to interact/modify another piece of code at specific, pre-defined spots. Learn more about hooks from here: https://developer.wordpress.org/plugins/hooks/

There are many hooks available in WP Job Openings plugin for template customization. If you just want to add some additional contents such as custom fields contents in the plugin template there is no need to override the entire template if the hooks are available within the template.