Document categories can be thought of as organizing your information by pratice area. As an example: Probate, Estate, Civil, Intellectual Property, Family Law. Within each category you can add sub-categories. Again, as an example, Probate may have sub-categories like: Summary Administration, Formal Administration, Homestead, Creditors, General/Miscellaneous.
Categories should be reviewed and created before adding documents. Categories can be added and edited at any time.