The business view is the part of the business model that applications will operate against, and end-users will see. The business view is nothing more than "buckets" (called categories) for you to re-arrange and re-organize your business columns in a fashion that makes sense to the consumers of the data.
In the business view, you can create any number of categories and arrange your business columns in those categories however it best suits your business, mixing and matching columns that derived from different business tables, even adding business columns more than once to different categories. The only restriction to the business view is that you cannot add the same business column more than once to a single category.