Population

Also known as 'Server Population', 'Server Pop' or just 'Pop', this term refers server population.

Depending on the context, the following populations are generally considered:
 * Current number of players online.
 * Total number of players on or offline.
 * Total number of possible player characters.
 * Total number of charachters created on the realm(that still exist)

Blizzard uses some unknown method to determine population on their Realm Status page, but the status indicator: