This is a list of modules added to Drupal 8 core. Not all modules are identical equivalents of the contributed modules you have known before.
|Module (or feature)||Notes|
|Action||Drupal 7 action|
|HTTP Basic authentication|
|Caption filter (part of
||Drupal 8 ships with the ability to align and caption images, videos, blockquotes and so on. The implementation is based on Drupal 7's Caption Filter module.|
||Makes the Drupal 7 contrib CKEditor module obsolete, but comes with a vastly simpler & better configuration UX, and much deeper integration.|
|Configuration Translation module||Successor to the Internationalization module as well as several glue modules from Variable, Internationalization views, Webform localization, etc..|
|Entity Reference module|
Provides the field type and a light API. No recurring dates or calendar functionality.
|Text Editor (
||A better integrated version of the WYSIWYG module that incorporates only the essentials.|
|There's email field with widget and 2 basic formatters in Core|
|Quick Edit (
||Provides in-place editing of entity fields. Has a Drupal 7 backport named Edit module.|
|Responsive Image (
||Formerly Picture in contrib.|
|Views||The most popular Drupal module was added as well as conversions of several blocks and lists to Views (including administration pages).|
See also https://drupal.org/node/2116417 for the modules/themes removed.