User blog comment:SsVivid/Evaluating Categories/@comment-24180511-20121024000741/@comment-4536066-20121024013456

Don't be misled about alignments; they're not black and white good-or-evil labels, and it's almost always assumed that the lines are blurred. Rather, more than anything, alignments identify a character's general set of priorities.

The Law vs. Chaos axis of the alignment is the juxtaposition of the ethical philosophies that either [everything in the world follows a natural order] or [life is random, chance and luck rule the world]. Law implies honor, trustworthiness, obedience to authority, and reliability. Chaos implies freedom, adaptability, and flexibility. Neutral, of course, is the reconciliation of these two beliefs.

The Good vs. Evil axis of the alignment is the justaposition of the moral values that either lead a person to [altruism, respect for life, and a concern for the dignity of sentient beings] or [harming, oppressing, victimizing and killing others]. Good in the context of the alignment axis implies that a person is willing to sacrifice to help others, while evil lacks compassion and has no qualms with victimizing others (regardless of if it's circumstantial or in active pursuit of harming them).

For more, I usually direct people to this page, because it explains everything very well.