A row is the UI representation that wraps an object form the ItemsSource of the RadGridView. The most commonly used class is the GridViewRow. There are also additional row classes that are used for more specific tasks, such as the GridViewGroupRow, which allows expanding and collapsing the items that belong to it. There are also rows that serve as a static containers - the GridViewHeaderRow and the GridViewFooterRow.
The RadGridView allows you to easily style the rows by exposing a style property for each of them. To learn more about styling the different rows read here.
The build-in mechanism for adding new rows allows you to easily insert data entries into your RadGridView. To learn more on that topic read here.
There is not a build-in mechanism for hiding rows. You can still hide or show rows by configuring a FilterDescriptor to filter the bound items by a certain condition. To learn more on that topic read here.
There are cases when you don't want to display the whole information that an object provides in a single row. The RadGridView allows you to define a details view, which can hold additional information provided by the row data item and is displayed only when the row is selected. To learn more on that topic read here.