Override css rules of a plugin within my own theme

Question

I want to override some rules of a plugin css file within my own theme so next time that I updated that plugin, my settings of that plugin be in a safe place . currently I copied that css file into my theme and changed some rules.So then I need to override this rules. I think found an answer that is related to my question (HERE) but I can't understand this code. how it works?

add_filter( 'style_loader_src', 'wpse106104_replace_stylesheet', 10, 2 );
function wpse106104_replace_stylesheet( $stylesheet_src, $handle ){
   if( 'plugin-script-handle' == $handle ){
        $stylesheet_src = get_template_directory_uri() . '/css/themes-copy-of-plugin.css';
   }
return $stylesheet_src;
}

Answer 1

The style_loader_src filter is used to modify/filter the src (url) of a stylesheet. The function callback accepts two parameters, the first is the original src and the second the handler of the stylesheet. The handler is the first parameter of wp_enqueue_style() used to enqueue the stylesheet.

So, to replace a stylsheet source with another one you should check the handler to know wchich stylesheet it must replaced, in the code you posted the checked handler is plugin-script-handle.