This Conditional Tag checks if the current post is a Sticky Post meaning the "Stick this post to the front page" check box has been checked for the post. This is a boolean function, meaning it returns either TRUE or FALSE.
<?php is_sticky($post_ID); ?>
is_sticky(); // When any Sticky Post page is being displayed. is_sticky('17'); // When Sticky Post 17 (ID) is being displayed.
is_sticky() is located in