There are times you may want to offer a product free of charge. Such as gifting it to someone or offering it as a promotional purchase.
To do this, you can create a price point of $0.
You may want to consider setting up as a campaign price so that your purchaser sees how much they are saving.
Note: The price doesn't have to be set-up as a secret price or coupon code but if you choose to add it as a list price it will be view-able on the normal order form for anyone to purchase free of charge.
If you have no intention of ever charging for the product we highly recommend you set up a list and create an opt-in form where people only give you their name and email address instead of purchasing through a zero price order form.