On personal computer (PC) systems, the VRM is typically made up of power MOSFET devices.
Modern video cards also use a VRM due to higher power and current requirements.
How the numerical codes map to supply voltages is typically specified in tables provided by component manufacturers.
Since 2008 VID comes in 5-, 6- and 8-bit varieties and is mostly applied to power modules outputting between 0.5 V and 3.5 V. The VRMs are essential for overclocking.
When a chip is pushed past its factory settings, that increases the power draw, so the VRM needs to match its output accordingly.