Drupal is world's leading open source content management system. Drupal8 is the latest release on it's journey. Already beta version got released with modern object oriented programming approach.
Below are the list of significant features added in the Drupal8 core.
Mobile in its DNA : Deploy content once and watch it in any device the way you want.
New Configuration Management: Manage configurations across different environments with ease
Better user experience: Serve your visitors with better experience by using Jquery autocomplete and modal dialogs.
Effortless Authoring: With WYSIWYG editor and in place editing, content authors can manage content very easily.
Views, out of the box: Many new features in views
Better markup with HTML5: The page markup in drupal8 is now html5-based.
Multilingual Capabilities: Translate any string in the system with built in interface.
Built in web services: Build mobile apps with drupal8 as your data source.
Fun and Fast Theming: Build sites quickly with flexible and secure twig template engine.
Field Power: Drupal8 provides more field types in core like email, phone etc..
Easier migration process from earlier version
So this will be the major release in drupal history with big change in it's architecture. Many useful Symfony (PHP based open source MVC framework) components are included in the drupal8 core and also included some third party PHP components and finally created a world class content management system.