You may have noticed when you are creating a new AdWords that Google sometimes suggest targeting multiple languages based on the location that you’ve targeted. Here's why you should consider additional languages for your Adwords campaign.
Campaigns that target a language are actually targeting the interface language in Google that a user has set for their interface. For example a Spanish speaker living in the United States may want to perform searches on www.google.com but has changed the interface language to Spanish. Alternatively, an English speaker living in Japan may want to perform searches on www.google.co.jp but see an English interface for their search and search results.
Google will only show your ad only if the user's interface language matches the targeted language in your ad campaign. This means that your ad won't appear when a user searches for one of your targeted keywords in the language that you're targeting, if the user’s interface is in another language.
For example, if you sell bicycles in the United States using the keyword bicycles, and you target only the English language, your ads won’t appear to bilingual users who search for bicycles but do so within a Spanish interface. Especially when targeting a geographic area with bilingual residents, targeting multiple interface languages can help your ad appear in front of as many potential customers as possible.