The American Heritage® Dictionary of the English Language defines Dandruff as:
"A scaly scurf formed on and shed from the scalp, sometimes caused by seborrhea."
Take a look at the various chapter previews to find out more information about specific areas of your scalp situation.
And for a full discussion of Scalp Disorders, we recommend purchasing a copy of Sylvia Sage's eBook - "How to Overcome Dandruff and Other Scalp Disorders".