CERN httpd: HEAD/PUT Method

I read on the CERN Server User Guide something about HHTP Methods.
I discovered some methods exists, such as HEAD, PUT, DELETE.
They were just mentioned. 
May some of you tell me something more about them (or tell me where 
to look for) ?

Thanks,
  Paolo
  *******************************************************
  Paolo VALENZA
  Dipartimento di Elettrotecnica
  Piazza L.da Vinci 32 - 20133 - Milano
  ph. (+39)-2-2399-3573 or (+39)-2-2399-3303
  Fax (+39)-2-2363561   or (+39)-2-2399-3587
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Received on Monday, 29 May 1995 04:36:20 UTC