Flight credits require that you use it to book another ticket - any destination, by the same person.

The surplus is then issued as a trip credit. Trip credits can be used against your future tickets or against tickets for others.

Say you use the $8500 flight credit and rebook it for you on a $1500 ticket. You will get a $7000 trip credit. You can use it for tickets for the entire family. Any surpluses continue to get issued as new trip credit. But the expiration will be the original expiration. So you must use up before then.

Updated to correct - trip credit.

All this can be done online. Trip credits require the original ticket number. Flight credits create new codes each time the surplus is issued. View the flight credit as a gift card.