Booking emails are now sent to the customer in the language that they booked online with. If they didn't book online, then the shop language is chosen.
See list of booking languages for the latest list.
The content of the emails can be customised for your shop. Go to Languages section and choose the "Customer Documents" option and then choose the language you wish to change.
Each of the properties refers to a piece of content, such as an email subject, title, column header etc in the actual booking email.