Humans are, by far, the most common race in the galaxy. Over the centuries, the differences between the old human races have begun to blur, and new distinctions have formed. Now, which one of the core three factions you were born into bares more weight on your core self than what part of old Earth your ancestors were born on.
Because Humans vary much more than other races, they have the unique ability to, at character creation, move one point from a base characteristic to another. This must be done before XP is spent on raising characteristics.
You have two choices when building a Human. Either you can pick one of the two Human races, or you can build a custom Human. Remember that picking either League or Terran is not picking your allegiance, it's simply picking which faction your family hailed from.
If you chose to build a custom human, instead of receiving a pre-assigned skill and then picking a single non-class skill to put a point into, you pick two non-class skills to put a point into. You still may not train these skills above rank 2 at character creation.