Polkit is a very badly-designed, poorly-executed imitation of UAC.

UAC is an operating-system-level system that heuristically detects when an executable is acting as an installer, and prompts the user with a Yes/No prompt (you can see screenshots online). This even works if you're running a terminal command. Terminal command needs administrator access? You get a blocking, modal dialog from the system that forces you to click Yes or No. That's very powerful.

Polkit is a component for controlling system-wide privileges in Unix-like operating systems, the manpage is less than 2 pages.