Continuum

Continuum transforms a Windows 10 Mobile smartphone (e.g., Lumia 950) into a full-screen, desktop-like PC experience when connected to an external display and peripherals.

Continuum, a feature introduced by Microsoft in 2015, delivered mobile-to-desktop convergence for Windows 10 Mobile devices. The core function: connect a supported phone, like the Lumia 950 or HP Elite x3, via a wired Microsoft Display Dock or Miracast, and the phone’s interface projects a full desktop environment onto the external monitor. This provided a familiar Windows desktop UI—including a taskbar and support for a keyboard/mouse—leveraging the phone's hardware. While it successfully ran Universal Windows Platform (UWP) apps at scale (like Word and Excel), its inability to execute traditional Win32 desktop applications limited its utility for many users, contributing to its eventual discontinuation with the Windows 10 Mobile platform.

https://learn.microsoft.com/en-us/archive/blogs/windowsmobile/continuum-for-phones-the-details