1. What is shortcode?
Shortcodes in Drupal are little bits of code that allow you to do various things with little effort.
2. How to enable shortcodes?
In Drupal, we can enable shortcode for each text format. Goto Configuration => Content authoring => Text formats and editors (http://yousite.com/admin/config/content/formats\), choose text format then click on Configure link.
Scroll down to "Enabled filters" section, check on "Shortcodes" then scroll to "Filter settings", click on "Shortcodes" tab. Check on shortcode, what you need to enable and click Save Configuration.