It allows specifying the theme-class to style rows.
In the Web environment, this property is available for the Table control, Responsive Table and Grid control classes in the Theme object. Depending on whether the Row Class property is for a Grid or a Table Theme Class, the classes to associate with it will be GridRow or TableRow, respectively. The Row Class property is also available for the Tables and Free Style Grid control at the control level.

Row Class property of the Grid Theme Class.

Row Class property of the FreeStyle Grid's row.
In Smart Device environment, only applies for Grid control classes and there are two differentiated properties: Odd Row Class and Even Row Class.
Objects: Web Theme object, Theme object, Web Panel object, Web Transactions
Controls: Grids, FreeStyle Grids (web-only), Table (web-only)
Platforms: Web(.NET,Java), SmartDevices(iOS, Android)