WP Post Thumbnail

<?php 
if ( has_post_thumbnail() ) { // check if the post has a Post Thumbnail assigned to it.
  the_post_thumbnail();
} 
 
the_post_thumbnail();                  // without parameter -> Thumbnail
 
the_post_thumbnail('thumbnail');       // Thumbnail (default 150px x 150px max)
the_post_thumbnail('medium');          // Medium resolution (default 300px x 300px max)
the_post_thumbnail('large');           // Large resolution (default 640px x 640px max)
 
the_post_thumbnail( array(100,100) );  // Other resolutions
 
?>