shortcodes is a cool feature to a WordPress site. You can do much stuff using the shortcodes. Galleries, videos, and various other functionality would require a lot of code editing. By using shortcodes the HTML and other markups are added dynamically directly into the post or page where the user wants them to appear.
Following is the basic example which you help you to understand the shortcode
Step 1. Insert Following code in file function.php file
$atts = shortcode_atts(array(
echo '<img width="' . $atts['width'] . '" height="' . $atts['height'] . '" src="' . $atts['src'] . '" />';
Step 2. You can access the above shortcode following way
Now implement same code as shown above step and check your output on the browser.