WordPress Theme

A WordPress Theme is a collection of files that defines the visual appearance, layout, and design of a WordPress website. Themes control how content is presented to visitors, without affecting the actual content stored in the database.

What Does a Theme Include?

A typical theme contains:

  • style.css – the main stylesheet, which also includes the theme’s metadata
  • index.php – the fallback template file
  • functions.php – theme-specific PHP functions and features
  • Template files like header.php, footer.php, single.php, page.php
  • JavaScript, images, and other assets
  • Optionally, templates for Gutenberg blocks or full-site editing (theme.json)

How Themes Work

WordPress uses a template hierarchy to determine which theme file to use for each type of page (homepage, blog post, category archive, etc.). Developers can override and customize this behavior by creating specific templates.

Customization

Themes can be customized via:

  • The Customizer (Appearance > Customize)
  • Theme options (if the theme provides them)
  • Full Site Editing (in block themes with theme.json)
  • Creating a child theme to override templates or styles without modifying the original

Example

If your theme has a single-post.php file, WordPress will use it to render individual blog posts. If not, it will fall back to single.php, and then to index.php.

Theme Types

  • Free themes – available from the WordPress.org theme directory
  • Premium themes – sold by developers or marketplaces like ThemeForest
  • Custom themes – built specifically for a single website or brand

Best Practices

  • Use child themes for customization
  • Keep themes lightweight and focused on design (leave functionality to plugins)
  • Ensure the theme is responsive, SEO-friendly, and regularly updated