A handful of modules have been added to Backdrop CMS core that were not in Drupal 7 core.
For a complete list of modules and the versions where they were added, see https://docs.backdropcms.org/documentation/features-added-to-core
The following is a much shorter list that includes only the modules that were included in Backdrop version 1.0.0.
- Admin Bar (port of Admin Menu)
- Views Bulk Operations
- Responsive table