Drupal Theming

a theme is a collection of files that define the presentation layer. Default regions are provided by the theme. A subtheme can add more regions and a unique page layout.

drush dl zen download to /sites/all/themes/zen

drush en zen enable zen

drush zen "Zen subtheme" zensub create a subtheme and give a machine name zensub

drush help zen

to create a page Drupal needs to make several database queries. To make it faster Drupal stores web pages in a cache, so in production clear the cache often.
drush cc all clear cache

• intro to Drupal theming
• subtheme

ref: bootstrap-themes documentation

navbar

the navbar will begin collapsed (and toggleable) in mobile views and become horizontal as the available viewport width increases.