What is a theme?

In simple terms, a theme is the presentational layer to content. Regardless of you working in Drupal or another content management system (CMS) without a theme, all you have is content that looks very similar to a Word document.

A theme generally consists of HTML markup, CSS, JavaScript, and media (images, video, and audio). It is this combination of technologies that allow the graphic designer to build something visually rich that can then be applied on top of the logic a web developer is building in Drupal. Sometimes, a web developer may be the person who implements the theme, but in most cases, you will hear the term themer or interface engineer, which describes the person who actually fills that role.

This book helps you learn that role. So, as long as you have a good knowledge of HTML, CSS, and JavaScript, you are well on your way to filling a much-needed role in the Drupal community.

We will begin by exploring the Appearance interface in Drupal 8.