Immortality is a state in which a being can theoretically live forever if not for accidents or murder. An immortal being cannot die from old age. To be immortal, one must never have died- a ghost can exist forever, but isn't immortal due to already being dead. Whilst vampires, although counted amongst undead, have never truly died, simply moved into a different state of being, and therefore are classed as immortal.
Whilst some races are naturally immortal, there are also cases of unique individuals achieving immortality through various means.
Examples of immortal races:
Examples of immortal beings: