Can someone explain this code to me ?

You need to look at the jQuery API documentation: jQuery API Documentation[^] Learning to read and use documentation for libraries is incredibly important when it comes to development. You'll need to learn to read and run code to work out how things work, if you expect people to explain things to you any time you get confused or don't understand something then you'll have a really bad time.

That being said, here's a breakdown of the code:

// When the document has finished loading, run function
$(document).ready(function () {

  // Find all links contained within elements with a class of "row"
  // Bind a function to when the link is clicked
  $(".row a").click(function (e) {

    // Prevent any navigation from actually happening from the link click
    e.preventDefault();

    // Find any <img> contained within an element with a class of "imgBox"
    // then update the "src" attribute (the path to the image) with the
    // location of where the link would have sent the user
    $(".imgBox img ").attr("src", $(this).attr("href"));
  });
});