A Recourse Loan means that the lender can keep chasing you for any money you still owe them, even after they have repossessed the home and possibly sold it at a loss.
In the US many states have non-recourse mortgages by law.
This means that distressed US homeowners can simply walk away and post the keys to the lender in what is referred to as "Jingle mail"
This means US lenders (primarily (80%) the US government) are on the hook for these mortgages.