Voluntary repossession means you give the lender your vehicle instead of the lender taking it.
An advantage to "voluntary repossession" is your lender will not charge you a repossession fee.
But, if the car does not sell at auction for the amount of money that you owe the lender, you will still owe the lender money. And the repossession stays on your credit report.
Is the lender saying you will not owe anymore if you hand over your vehicle? Is the lender saying the repossession will not be on your credit report? Get these promises in writing before you give the lender your car or truck.