Choose the default language that your booking confirmations will be sent in. 

In Supported languages you can add other frequently used languages by your guests. Example: Your default language is English, meaning that your guests will receive English booking confirmation if their country´s language is not selected in Supported, or if no country is chosen while making the booking. 

In case you add i.e. Spanish into your Supported languages, your guests from Spanish speaking countries will receive a booking confirmation in Spanish. 

FYI all of your written text will need to be manually translated in all of your supported languages for the guest to receive all of their details in that language.

Additional info regarding languages:

In other categories of Settings you can use the language setting and add custom texts in your selected supported languages (in this example Spanish), see buttons circled yellow in the example below on Guest Registration Form. To summarize; everything that you manually write yourself in the system you will also need to write in the supported language if you want that text to be in that language.