Human-Machine Interface (HMI) is the hardware or software through which an operator interacts with a controller. An HMI can range from a physical control panel with buttons and indicator lights to an industrial PC with a color display running dedicated HMI software. Human-machine interface technology has been used in different industries like electronics, entertainment, military, medical, etc. Human-machine interfaces help in integrating humans into complex technological systems. Human-machine interfaces are also known as man-machine interfaces (MMI), computer-human interface or human-computer interface. HMIs are often seen on printers, your GPS, or even inside one of the new Teslas.
Source: NIST SP 800-82 Rev. 2
Additional Reading: Bardstown Bourbon Upgrades HMI for Strategic Connectivity