Are you in CA?

It means wife own the property with you, but not on the mortgage.  Sometimes if one person's credit/income is not enough, he'll have to add another family member on the mortgage so bank has to get their credit/income.  I assume you just want to add your wife's name on there. You should just ask the loan officer what it means, instea of asking us to guess for you.  

Advantage: your wife won't be mad with you.

Disadvantage: they need your wife's consent to sell, but if you are in CA, you need her signature to sell anyway.