JQuery selector running time

How does JQuery selector works internally? Is it a js getElementById kind of function? What's the running time in order to fetch an object from the DOM?

For example:

<html>
  <div class='container'>
      <div id='myID'> 
         <p class="myText">My Text</p>
      </div>
  </div>
</html>

And this JQuery code:

$(document).ready(function(){
   $("#myID").click(function(){
       $("myText").hide(); //Running time?
   });
});