Checkout process and Email

I am trying to customize my checkout process. I wanted to collect a confirmation email ( I am guessing this means that if my customer wants a confirmation email about his order they need to input it into this field) However there is already an email address field. I don't want to collect the email address twice. If I just collect the email address that the checkout process asks for will my customer be able to get a confirmation email?

The order confirmation email is sent automatically by HikaShop when the order is confirmed. It uses the email address that the user entered when he registered during the checkout.

I don't see why you want to ask for the email address a second time ?