Thanks; after much gnashing about, I figured out what it was that I
didn't know. ps's guess in the previous post was exactly right; my
registrar was hosting my domain, and simply forwarding requests to my
static IP.

I assumed (wrongly) that setting up the DNS information was part of
the registration process; I assumed it would go something like this:

1. choose a domain
2. register it
3. tell them my IP address
4. set up my web server on my local machine
5. tell people to visit my new domain

I knew how to do the last two steps well enough, and the first two
were simple, just a matter of following instructions. However, I
thought it odd that they never asked me for my IP address during the
domain registration process. I figured I'd have to go and do that on
their website, and the only thing I found remotely close was "Domain
Forwarding", which I completed. I thought that was just how it was
done.

I now realize that "Domain Forwarding" is not the same thing as
associating my IP with my domain name in DNS; that what my registrar
does is to associate _their_ IP with my domain name, and that they
don't provide DNS for the address I just registered through them.

They did answer my question quickly enough when I figured out what to
ask them - Q: "where do I associate my IP address with my domain
name?"
A: "We do not provide that service. Try www.zoneedit.com"

Which I did, and through which I now have an IP Address (A) Record
directly connecting my IP to my domain name.

It's interesting; I know a fair bit about computers and setup (for an
amateur), but in this case didn't even know where to look to find out
what questions I should be asking - and therefore didn't find the
answers.

B.