Composer can be used to manage more than one website at a time, including sub-sites that exist within your organization's main website.
Each individual site is referred to as a "domain" (website names, such as "finalsite.com," are called domains when created, bought, and sold). Each domain that your school controls can be added to Composer and managed independently.
Clicking on a domain will reveal its contents for editing.
Domains are organized into "pages" and "branches." Pages with “sub-pages” saved under them show a small triangle icon (you can click that triangle icon to reveal any sub-pages without having to select the parent page). Branches are shown in gray and have a small “branch” icon along their left-hand edges.
Clicking on any branch, or on any page with sub-pages saved beneath it, will expand that section and allow you to select any sub-pages saved there.
Branches allow you to organize site content logically without impacting the site's structure. Branches do not affect the web addresses of pages saved within them. They are strictly for organizing pages on the back end of your site. Note that pages do not have to be saved within a branch.