- "bootstrap.css" is a build of Bootstrap based on the standard Bootstrap style-guide. It can be used with other CiviCRM extensions which satisfy the Bootstrap style-guide.
- "custom-civicrm.css" is an optional replacement for "civicrm.css". It uses the same visual conventions and SCSS metadata, but it applies to existing core screens.
For more information, see https://github.com/civicrm/org.civicrm.shoreditch.