Khuld is translated: everlasting, eternity, and also immortality. This word can refer to both living or non-living creatures. For example consider two Ayah below, in which Khuld referes to non-livings things:
And this is an example of the reference to living people:
Yamut means dies and La Yamut means does not die. They can be used only for living things, because dead or aliveness do not make sense for non-living objects. Allah is the only one who does not die, so La Yamut can be used only for Allah: