My servicer offered me a shared appreciation mortgage as a means of modification. What does that mean?

Depending on how your home value changes over time, the lender’s share of the value of your home might be worth more than the balance you owe on the loan. Because you give up part of your future gains, the interest rate and monthly payments on your loan will typically be lower than the market rate for other types of loans. The lender will collect its part of the increase in your home value when the loan is repaid.