Use language targeting to target people based on their language.
How does language targeting work?
Open a line item, navigate to TargetingLanguage then select one or more languages to target or exclude (note you can only target languages by inclusion or exclusion, not both).
Display & Video 360's language targeting targets impressions based on the languages of an individual bid request, which are specified by publishers. Publishers can set the languages of bid requests based on content, user, and other factors.
In cases where a publisher hasn't specified a language, Display & Video 360 uses a combination of content- and user-based signals to infer the likely languages for an impression.