The Replacement of the Serial Enumeration Service (often referred to as "SerialEnum" or "Serial Enumerator") in Windows is a system service or driver that manages the detection and enumeration (i.e., the process of identifying and assigning a port number) of serial devices that are connected to a computer via COM (communication) ports. These serial devices could include hardware like USB-to-serial adapters, legacy serial ports (RS-232), and other serial communication peripherals.