To start using “People” options in your bookable products, you have to enable the People module from YITH > Booking > Modules.
Now, from YITH > Booking > Configuration > “People” you can create new person types.
You will only have to add the name of the person type and the description (if needed), and you are done. These texts are not visible to customers.
For more information on how to use these person types in your bookings, go to this page here.