A classification is a way of categorizing Analytics variable data, then displaying the data in different ways when you generate reports. You establish a relationship between a variable value and metadata related to that value. Classifications can be used on most custom dimensions, such as Tracking code, props, and eVars.
Classification sets are the primary way to classify data. Classification rules and the Classification importer are legacy methods to classify data. All classification data ultimately operates the same in reporting; you can combine any of these methods to best fit your organization’s workflow.
A single dimension can have multiple classification dimensions. For example, you can classify Product IDs with additional product attributes, such as product name, color, size, description, and SKU. Each of these attributes would be a separate classification dimension belonging to the same parent dimension. Augmenting your reports with these attributes provides deeper and more complex reporting opportunities. Once a dimension contains classification data, the classification dimension is available in reporting that contains only classification dimension items. Any parent dimension item that does not contain a classification value is grouped under Unspecified