While forbearance can offer temporary relief from the costs of your mortgage payments, it doesn't mean you're off the hook. Your payments aren't waived or forgiven. Rather, they are on hold during the forbearance period. You still need to eventually repay the forbearance in full, but that doesn’t have to happen all at once.
The goal of forbearance is to give you time to resolve the issue that is causing you to be unable to pay your monthly mortgage payments. Once that issue is resolved, or once the forbearance period is over, you are expected to pay back what you owe at the end of your loan. Talk with your servicer about how to best repay the payments you missed. Options could include a repayment plan or a loan modification.