File Entity (or fieldable files) is an easy Drupal 7 solution allowing you to add files over the web interface without FTP (if admin/content/file is missing, install the File Entity module).
File entity provides interfaces for managing files. It also extends the core file entity, allowing files to be fieldable, grouped into types, viewed (using display modes) and formatted using field formatters. File entity integrates with a number of modules, exposing files to Views, Entity API, Token and more.
If you are using the Drupal 8 file_entity you should use the core media module instead of file_entity. The new migrate_file_to_media module provides a decent way to migrate your old-fashioned file and image fields to media entities in Drupal Core. See Migrate File Entities to Media Entities in Drupal 8.