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There are three kinds of add-ons for your Backdrop site: Modules, Themes, and Layouts.

 Each type of add-on can fall into one of three categories: 

  • Core - included with the Backdrop CMS.
  • Contributed - downloaded from backdropcms.org (or by using the Project Installer module)
  • Custom - code that you have written yourself.

Modules

A module is software (code) that extends Backdrop functionality.

Creating custom modules requires a thorough understanding of PHP programming, and Backdrop's APIs (some HTML & CSS knowledge is also helpful). Find out more about creating modules at https://api.backdropcms.org/developing-modules.

Themes

A theme sets the design for the website.  

Themes are usually responsible for the typography, color scheme, page width, etc, and most heavily influence the the look & feel of your website. Think of a theme as a Skin for your Backdrop site: the theme can be changed at any time, but the rest of your site should remain intact.

Creating custom themes requires a thorough understanding of HTML, CSS, and Backdrop's theme layer (some PHP knowledge is also helpful). Find out more about creating themes at https://api.backdropcms.org/developing-themes.

Layouts

Layouts determine how (and when) different items are arranged on the page. 

A single two-column layout can be used for every single page on your site, or a special three-column layout could be used on only the home page. If you need a different arrangement for pages than for posts - or a different menu added into the sidebar - layouts will help you set this up.

Creating custom layouts requires a thorough understanding of HTML, CSS , and Backdrop's theme layer (some PHP knowledge is also helpful). Find out more about creating custom layouts at https://api.backdropcms.org/developing-layouts.