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Within every faction there are also a large number of corporations, both NPC driven and player owned. There really aren't a lot of differences between the various NPC corporations as far as game play goes - it's mostly just a backstory and role-playing difference. As a character in the world of EVE, you have relationships with both players and NPCs, and therefore you also have standing with their respective corporations. (You can manually adjust your likes and dislikes for players and player controlled corporations through the UI as well.) Besides the obvious (that a player or NPC who doesn't like you might just kill you), these standings are also used to determine which missions you can get and when.
