Displaying data in the RadGridView depends on the data binding mechanism. The entry point for the data to be bound is the ItemsSource property, which you must set in order to display data in your RadGridView control.
this.radGridView.ItemsSource = GetObservableObjectData();
Me.radGridView.ItemsSource = GetObservableObjectData()
The next step is to configure the data bindings for the RadGridView columns. To learn more about the data binding in the context of the RadGridView take a look at the Configuring the Data Bindings topic.
After the ItemsSource is set, the RadGridView continues to internally load the data. The same loading finds place when filtering, sorting, grouping and etc.
To learn more about data binding and find answers to your questions take a look at the following topics: