what's with pulseaudio

[Steve Kleene <skdeb@syrano.acb.uc.edu>]

Sometime in the last month or two a regular upgrade of my Wheezy systems
caused them to start running /usr/bin/pulseaudio.  Related directories popped
up, including:

  /.pulse
  ~/.pulse
  /tmp/pulse-tHdn2FVycDvX (e.g.)

as well as these files:

  /etc/rc3.d/S02pulseaudio
  /.pulse-cookie
  ~/.pulse-cookie

Did pulseaudio replace some other audio system?  If I shut it down will I
have no sound?  (I'll try this if no one happens to know the answer.)   And
what's in these .pulse-cookie files?  I'm leery of anything with "cookie" in
its name.

Thanks.