Media entity provides a 'base' entity for a media element. This is a very basic entity which can reference to all kinds of media-objects (local files, YouTube images, tweets, CDN-files, ...). This entity only provides a relation between Drupal (because it is an entity) and the resource. You can reference to this entity within any other Drupal entity.
This module further provides some example Form Display widgets and Display widgets to use this entity from the referencing entity. This module also aims to make the creations of new widgets as easy as possible.
This module attempts to provide the base module for the D8 media ecosystem. It aims to combine the best of D7 solutions such as:
This project/initiative was started at DrupalCon Prague. See report for more info.
Full featured media solutions
This is more or less an API only module. If you need full-featured media experience solution you need to install one of the modules that provide sane default configuration. Take a look at Media Pinkeye.