Can be used to translate hardcoded texts in your theme, using locale files. It expects you to put a .yml (YAML) file for each language of your site in the locales folder. So if your site supports Dutch and English, you should have the following files:

locales/nl.yml
locales/en.yml

These files can then contain translations, given that you keep the same data structure. For example:

locales/nl.yml

footer:
  heading: "Welkom bij de footer"
  served_by_plate: "Deze website wordt geserveerd door Plate"
  contacts: 
    phone: "Telefoon"
    email: "Email"

locales/en.yml

footer:
  heading: "Welcome to the footer"
  served_by_plate: "This site is served by Plate"
  contacts: 
    phone: "Phone"
    email: "Email"

When these files are in place, you can use the translate filter as follows.

On the Dutch version of the site:

Input:

{{ "footer.heading" | translate }}
{{ "footer.contacts.phone" | translate }}

Output:

Welkom bij de footer
Telefoon

On the English version of the site:

Input:

{{ "footer.heading" | translate }}
{{ "footer.contacts.phone" | translate }}

Output:

Welcome to the footer
Phone

Warning: When using ‘yes’ or ‘no’ as key values, YAML parses this as true or false. You have to escape the key value with quotes. See following example:

language:
  'no': "Norks language"