In Drupal 8, you can put text in certain defined places in various YML files, and it will be picked up as translatable strings and translated automatically:
Module names and descriptions in
*.info.yml files are still found as translatable in /admin/config/regional/translate.
_title (coupled with optional
_title_context) key values under the
defaults section of
*.routing.yml files are found in translatable in /admin/config/regional/translate.
title (coupled with optional
title_context) key values in
*.links.contextual.yml files are found as translatable in /admin/config/regional/translate.
That these strings are found as translatable (and later on
t()-ed in the process of handling them) also means that any code generating them dynamically should take care of not translating them too soon.
For example, if you need dynamic titles in your local tasks or actions, extend the base class and override the
getTitle() method to run the translation the right way.