Well, the difference between black hat and white hat is that white hat generally sticks to whatever quality guidelines
Google has.
Also, black hat involves pushing the envelope as far as link generation and bending the rules go.
This involves creating all sorts of accounts and buying and selling links, that kind of thing.
White hat, generally speaking, tends to stay away from that and falls a more within the range of practices Google
condones.
With that said, a lot of this distinction is actually kind of illusory.
If you are going to go strictly by Google's definition of how it expects links to materialize all over the internet,
then pretty much anything, any practice that involves purposeful or intentional efforts to create links is black hat.
In my mind, this is really a question of degree, not necessarily quality.