For a generic, vanilla ZenCart installation, with
no special, customized features programmed in
on our ZenCart side (just the ordinary, out-of-
the-box install that's done from the start),

1) do I even need to have IPNs activated, or
2) are the IPNs the method by which basic
purchase confirmations are communicated back
and forth between ZenCart and PayPal?

PayPal allows a setting to disable IPNs if I don't
want them. Again, I'm not clear on the purpose
of the IPNs. Were I to disable IPNs, would I
effectively shut down our online shopping
service? :-\

*sigh*