If you don't reach your funding goal when your campaign ends, you may want to fulfill the orders your backers paid for, otherwise, you need to refund those payments to your backers.
Fundlify has created a unique solution to this problem, you can choose a campaign and include the Commits phase (reservations) before you start taking pre-orders and collecting payments from your backers. During the Commits phase, only emails are collected and demand can be accurately assessed, if you hit your Commits goal, then most probably you're going to hit your pre-order goal, you can confidently start taking pre-orders and collecting payments, it's important to keep an eye on how many days you want to run your pre-order phase for.
If during the pre-order phase you don't hit your goal, you can simply not capture your backer's payments. This is if your store Payment Authorization is set to "Manually" which means you can manually capture those payments within a limited time called Authorization Limit, which is usually 7 days, not capturing payments will release the lock on those payments. which essentially means you don't have to issue Refunds.
if Payment Authorization is set to "Automatically" it means that those payments are automatically captured and in that case, you're going to have to refund payments to your backers if you're not going to fulfill their orders.