In any Payment Information section, within a form such as Ticketing, there is a selection called Payment Section Visibility. This allows you to have a form that can be submitted with or without a monetary value. For example, if you had a ticketing form that offered both Free and Paid tickets on the same form, this function will make that process easy.
By putting a check beside "Hide the payment information section unless the Total Amount is greater than $0.00." then the payment section asking for a credit card or PayPal will not appear if the amount is $0.00, so your supporter can still enter their information and order free tickets. The Payment Section will appear any time the total is more than $0.00, such as with the purchase of a paid ticket, adding a donation to the order form, etc. so your supporter can process their payment.