The Translation Overview page provides a table listing the site's nodes and showing what's been translated into each language. It also lets you assign priorities for translating nodes into the various languages.
For translations of taxonomy terms and menu items check out the Translation table module.
The current maintainers won't port this module to Drupal 8. The superseding Translation management (TMGMT) module was initiated with Drupal 7 and is already well ported to Drupal 8. We highly recommend it - already with Drupal 7.