Widgets are mini-apps (e.g., weather, clock, calendar, etc.) that can be added to a Home screen. They aren't the same as shortcuts as they generally display info and take up more space than a single icon.
From a Home screen, tap and hold any open space (where no shortcuts or widgets are present).
From the Widgets tab, tap a widget.
The widget is placed on the selected screen. To move the widget, tap and hold then drag to the desired location.