Category
In Chart Views, categories classify chart values for comparison purposes. Categories and their values correspond to group rows and grouping values in tabular Views.
A category displays one or more related chart values. The number of chart values displayed per category depends upon the diagram type (a simple or multiple diagram).
Default categories display chart values at the highest data level and provide a simple classification of chart values without aggregation. In terms of databases, default categories stand for a data column, which uniquely identifies and refers to the values within a data record.