Hertz is a new name for 'cycles per second' this is a analog concept. It is abbreviated both as Htz and Hz. Baud originally referred to a change of states, e.g. high to low. But it falls apart technically when used for these high speeds. Bits per second refers to '0' and '1' in any order or combination, which is digital.
Bytes are sets of eight bits.
Also a digital concept. And kHz thousand cycles per second, for analog modems. Not the baud rate. This is analog, or a sine wave pattern. The request is so short that the frequency is quickly available again for some other PC to use for its own request.