How can I send data or event info from Javascript to Default.cs (Asp.net)?

How can I send data or event info from Javascript to Default.cs (ASP.NET)? is it ajax?

From stackoverflow

• You will need to create an AJAX call to Default.aspx.

  Using jQuery:

  $.ajax({
      type: "POST",
      url: "Default.aspx",
      data: "first=John&last=Doe",
      success: function(msg){
          alert( "Data saved: " + msg );
      }
  });