Learning about BL

Could someone point me to a source where I can learn about brushless systems. I am very new at this...kv, cogging and so forth, I have no idea as to what it means. I don't even know what makes an 8 turn different from 9 turn. Is there a source that goes over all of this stuff so I can learn what it means?

BTW, what does cogging mean?

Thanks for all of you help....I never would have gotten this far!