I get 4th Soft reject with event delegation

Hi everyone,
I get soft reject with

  1. PROPER EVENT BINDING: Consider using the preferred .on() method rather than .click(), .bind(), .hover(), .load(), .ready(), etc. For best performance and concise code use event delegation whenever possible: https://codepen.io/32bitkid/post/understanding-delegated-javascript-events

I fixed that on() stuff but i cant understand event delegation.
that’s my code i want to make with event delegation please :

	// This will change the color of label in the portfolio Section
$(".portfolio ul li a ").on("click", function () {
	var PortfolioListItem = $(".portfolio ul li a");
	PortfolioListItem.removeClass("active")	// remove class from others
	$(this).addClass("active");	// add class for the clicked one
})

});

Your code is correct now (as asked by reviewer). I assume you’ve used $( mySelector).click( function() { }) before.
More:
.on() method - http://api.jquery.com/on/
.click() method - https://api.jquery.com/click/

Also .on() can work with dynamically added DOM elements or you can unbind event handler by using $(mySelector).off( ‘click’)