Normal and sub-item categories
Normal categories are those that create the hierarchical browse structure in the Customer Center. They might also be used to establish discounts and campaigns. Sub-items can be drawn from any standard browseable or non-browseable item category.
For example, if your company sells a computer system with a hard disk that is also available separately, but with a wireless networking card that can only be purchased with the system, then the hard disk would belong to a browseable category. The wireless-networking category would be set to "non-browseable" and its item as "sub-item only" (since this type or item is not available separately).
Often, when a standard category will be used to establish attributes for a complex item, that category will contain items that can be used with any given parent item. For example, only a few of the hard disks available in the catalog might actually be compatible with a given computer system due to size, connection standards, formatting, etc. This is not a problem because when you add a sub-item category as an attribute to a parent item, you will specify which item from that category will be available with the parent. .
In the B2C setup, you can apply individual styling for top categories and sibling categories.