The File Preview widget allows users to view the file contents on a form of a task or an app item. When you set up this widget, you must specify the context variable/app property of the File type.
The Row widget is used as a container for other form elements. Inside the widget, you can place other widgets and variables from the Properties tab.
The Standard Item Form widget displays the app item properties that were added when configuring the form. This widget is by default located on the form when you open it for editing.
With the Upload and Preview File widget, you can add a file to an app item form or a task form, and users will be able to view its contents.