Drupal themes represent the components of a Drupal site that render content on any browser equipped device in a visually appealing fashion. If Drupal is the cake, then themes are the frosting and decoration—they make your web site beautiful.
The art of theming requires a mixture of visual design skills, including using tools such as Photoshop, as well as experience in developing HTML markup and cascading stylesheets (CSS), using JavaScript, and using the Twig templating engine to connect the theme to the output generated by Drupal.
This chapter covers the details of the role of a Drupal theme, ...