Population Status is a classification that is used to estimate the total population and/or conservation status of a given species (usually only used for non-sapient creatures).
Extinct: Members of this species no longer exist.
Near extinct or critically endangered: This species is extremely rare, and only very few members remain.
Rare or endangered: This species is very rare, and has a good possibility of becoming extinct in the near future (perhaps due to an immediate threat or something hindering reproduction).
Vulnerable: This species, though not in any critical danger, is still liable to becoming extinct in the future (usually because of some long-term threat).
Common: This species has a healthy population; this is by far the most common status.
Abundant: This species has a very high population.
Overpopulated: This species is dangerously overpopulated or reproducing rapidly and expanding out of control.