Does one have to have an index.htm or html page on their site? Or could the index page be .php?

Hi Jenni,
No you dont need a index.html, index.htm if you have an index.php

It can be almost anything that you want. Usually your hosting company has some defaults like:
index.htm
index.html
index.php
index.asp
index.phtm
index.phtml
default.htm
default.html
default.asp
default.phtm
default.phtml

There are others, but usually these are the main ones. Even if you need it to be something else, your hosting company should change it for free.