https://learn.microsoft.com/en-us/dotnet/api/system.windows.controls.itemspaneltemplate?view=netframework-4.8.1&redirectedfrom=MSDN
ItemsPanelTemplate Class (System.Windows.Controls) | Microsoft Learn
Specifies the panel that the ItemsPresenter creates for the layout of the items of an ItemsControl.
class systemwindowscontrolsmicrosoftlearn