Taking a further advance on an existing mortgage to access some of the difference between the value of your property and your current mortgage. It is a way of unlocking the value of your property, without having to move home. It is used mostly by older homeowners who either have paid off their mortgage altogether or have only a small amount left to pay, and require a lump sum or a regular income (or both).
If you live in the property until you die, the money from its sale will be used to pay the lender before anything left over is paid to your beneficiaries. If you sell the property before you die, you will need to repay the money you borrowed from the lender. With some types of loan you might also have to make regular interest payments.