While only the system administrator has access to set the locale for the client, users have access to change their individual profile view. Setting a locale for a user profile displays all translated Product Catalog values in that locale for only that user's UI display.
Setting a user profile locale only affects the display of Product Catalog values in the Aria UI. It does not affect the display of Product Catalog values for customers.
For example, if you create an account in a French locale, that account will display Product Catalog data to your customers in the configured French translations. Likewise, if you create another account in a Danish locale, that account will display Product Catalog data to your customers in the configured Danish translations.
If you then set your user profile to a Spanish locale, the accounts created in French and Danish locales will still display Product Catalog values in the French and Danish translations for customers, respectively. However, now both accounts (and all other accounts) will display Product Catalog values in the Spanish translations in the UI.
If translated values have not been entered for the set user profile locale, the Product Catalog value will display in the client locale (the client locale is set to English by default).