You can find the Invoice and Quote templates in the same location as the rest of your templates.
These templates create the email your customer will receive when you issue and email an Invoice or Quote. The email can be edited prior to sending, so the template provides a baseline.
You can see that there are three important boxes at the top of the page.
The first box sets whether the reminder will be sent automatically or not.
The second box sets whether or not a copy of the email will be sent to you.
The third box sets how many days after the Invoice/Quote was issued to send the reminder.