In Salesforce Knowledge, data categories are a set of criteria organized hierarchically into category groups. Articles in the knowledge base can be classified according to multiple categories that make it easy for users to find the articles they need. For example, to classify articles by sales regions and business units, create two category groups, Sales Regions and Business Units. The Sales Regions category group could consist of a geographical hierarchy, such as All Sales Regions as the top level, North America, Europe, and Asia at the second level, and so on up to five levels. Authors assign categories to articles. Administrators can use data categories to control access to articles.