Advanced (4 RP)
Prerequisites: Advanced or monstrous power level.
Modifiers: Pick either mental or physical ability scores. Members of this race gain a +2 bonus to all of those scores, a +4 bonus to one score of the other type, and a –2 penalty to one other ability score of the other type.
I have looked around but I can't find out precisely what the Prerequisite is checking for. Can someone explain?
It is a reference to the Power Level of the race on 214 of the same book.
All of the races presented in the book that are meant to be played as PCs are Standard. There are, however, other races in places like the Bestiary that are significantly more powerful, Monstrous. There are guidelines for creating both, and ones in the middle, Advanced, though you see the fewest Advanced.