Keyboard multiplexing?

[Ernst de Haan]

The Handbook, section 8.4 reads:

    device          kbdmux        # keyboard multiplexer

    Basic support for keyboard multiplexing.

Question for me remains: "What _is_ keyboard multiplexing." I did  
some searches on Google and Wikipedia, but I found no clear  
definition, so IMHO an explanation would provide added value,  
answering the following questions:
1. what is it?
2. when is that useful?
3. can I remove it if I don't use the machine as a desktop?

Cheers,


Ernst