This is just a curiosity but I would like to have some understanding of what is going on.

I am just getting started with the Teensy 3.6 and very pleased with the Mouse.ino example. It works well and I have used it with a terminal emulator (ZOC) on MacOS to record the keycodes for every key press. I had to comment out the "wait for Arduino Serial Monitor" since I am not using that tool and realized that was why nothing seemed to work at first.

I have one dumb question and assume the answer is some basic piece of information that I am missing. I have read on PJRC the following:
Serial.begin( )
Initialize the Serial object. The baud rate is ignored and communication always occurs at full USB speed.

I do not find Serial.begin used anywhere in the sketch, which is part of my confusion, but the main thing is: how does the terminal emulator know to ignore the baud rate that I configure it for? I suppose it must somehow detect that rather than a FTDI type of interface it is the full USB speed interface? Pretty handy in any case.

I tested it on Ubuntu with PuTTY to make sure PuTTY is also "happy" at any configured baud rate.

I will appreciate any information to help me understand this.