Mozilla launched Fluent, a new standard for applications to offer i18n (internationalization) of their user interfaces.
Rather than the very basic 1:1 translation many i18n packages offer, the aim of Fluent is to accommodate the arbitrary grammar requirements many languages can have.
If you’ve studied other languages, you know that many of them have gender pronouns and differing ways of saying certain numbers.
Fluent allows developers to accommodate these differences without having to hard code any rules into the code.
For a more detailed article on use cases, you can read Mozilla’s launch announcement.