With this type of mortgage you are only paying interest each month. This means that although your payments will be lower, the amount you borrow will still be outstanding at the end of the mortgage term. You'll need to make alternative arrangements to pay off the mortgage to avoid the property having to be sold, such as taking out an ISA.
A mortgage is a loan secured against your home. Your home may be repossessed if you do not keep up repayments on your mortgage or any other debt secured on it.