Scammers have taken an old browser scam and invigorated it using a clever and new tactic that takes advantage of your web browser’s full-screen mode to show a fake Windows 10 desktop stating your computer is locked. This type of scam is called a police browser locker which pretends to be law enforcement locking your browser because due to illegal activity. These scams then state that if you pay a fine via a credit card, it will unlock your computer so you can use it again. These types of scams are normally easy to detect as they utilize fake and suspicious URLs.
Source: https://www.bleepingcomputer.com/news/security/fake-windows-10-desktop-used-in-new-police-browser-lock-scam/