I had the same question and I found this page. And the answer is in @zipzit's comment. So I post it as answer here:
To see "Com Ports" in Device Manager in Windows 10 you should select "Show hidden devices" in View menu.
A COM port is simply a serial communications port. It can have a physical external port, or can connect to an internal device to provide a simple interface for software to use.
In your case the COM port connects to a motherboard management interface, in order for a software tool to manage your motherboard firmware.
"Old" COM ports used a UART that was physically connected to the CPU BUS and used memory addresses to communicate with the CPU. These addresses got associated with particular COM ports so that they were consistently given the same port number.
USB is a protocol rather than a CPU addressed device, as such there is no way to know that one device being plugged in is the same as a previous device. As a result the USB device may get a different identifier when plugged into a different socket and as a result Windows will assign it a new COM port.
How many COM ports there are depends entirely on your system. A modern system may have none at all. A system with USB to serial converters could have hundreds. It depends.
