What does a special set of tags <?= and ?> do in PHP?

<?= and ?> tags called as short tag in php .

 The output is displayed directly to the browser.
<?=  only works if PHP's short open tags is turned on.
 ?> is  PHP closing tag.

 Example:
<?
PHP code ...
?>

PHP Syntax:
<?="Hello Rajesh Sharma!"; ?>
<? echo " Hello Rajesh Sharma! "; ?>
<?php echo " Hello Rajesh Sharma! "; ?>
<?php echo " Hello Rajesh Sharma! "; ?>

 is the same as:

 <?= " Hello Rajesh Sharma! " ?>

Note: <?= is shortcut for echo;