whats $_POST in jquery code example

Example 1: $post in jquery

$(function(){
    $('#myForm').on('submit', function(e){
      e.preventDefault();
      $.post('http://www.somewhere.com/path/to/post', 
         $('#myForm').serialize(), 
         function(data, status, xhr){
           // do something here with response;
         });
    });
});

Example 2: jquery $.post

// Assign handlers immediately after making the request,
// and remember the jqxhr object for this request
var jqxhr = $.post( "example.php", function() {
  alert( "success" );
})
  .done(function() {
    alert( "second success" );
  })
  .fail(function() {
    alert( "error" );
  })
  .always(function() {
    alert( "finished" );
  });
 
// Perform other work here ...
 
// Set another completion function for the request above
jqxhr.always(function() {
  alert( "second finished" );
});