Summary
Power Automate for desktop uses UI elements to interact with local application UIs and windows. These UI elements allow flows to identify parts of the UI without the system having to resort to image recognition or absolute coordinates.
UI elements can be added from the flow designer's UI elements tab, or directly from a relevant action's properties; they can then be used as input in UI/Windows actions.
UI/Windows actions interact with entire windows or elements within them. Such actions can be used to provide input to, extract data from, or manipulate various aspects of UI elements.