When you add an extra product option/field it gets displayed in multiple places. The following screenshots shows the different places where you can see the extra fields and the input provided by the customer.

Product Details Page

extra-option-product-page  

Cart Page

extra-option-cart-page  

Checkout Page

extra-option-checkout-page  

Order Confirmation Page/ Email

extra-option-order-confirmation-page  

Order Details Page

extra-option-order-details-page