A nonplayer character or NPC is an entity in the game that is not under the direct control of a player.
Although most often thought of as player-interactable entities such as agents and rats, NPCs can take any of a huge variety of roles. Other examples include rogue drones, CONCORD and racial navy ships, jump gate defense batteries, nonplayer corporation officers, and the dozens if not hundreds of other types of non-player owned ships flying around in space. Even player-controlled drones are to some extent able to be considered NPCs.
There are various ways of earning ISK based on the NPC characters.
The most common way of doing so is by performing missions for NPC agents found inside or outside of stations.
When a player kills a NPC rat, its bounty will be automatically transferred into the player's or his fleet's wallet. As an exception, Rogue Drones do not have bounties, their wrecks will leave behind precious minerals instead.
Besides the bounty, NPC rats will also leave a wreck after they die. Any player can loot the wreck, collecting any items that are found in it. However, only more experienced players can salvage the wrecks, recovering rather expensive pieces of equipment used to build rigs.
Found only in wormwhole pockets, these NPC rats are very powerful and offer higher rewards.