I was looking at installing Exchange 2010 on the Internet and one thing in my research that came up was, you must have an Internet-Facing Active Directory site.
What does that mean? All I have is an Intranet, one forest, one domain. None of it is on the Internet. I don't know what I'd have to do to put AD on the Internet.
I don't know where you got this information from, but either the website you got it from is misinformed, or you misunderstand (more likely).
You do not have to have your Active Directory servers directly connected to the internet (don't EVER do that by the way). What it means is that you must have an Active Directory site that has internet connectivity, typically through a router and preferably through a firewall too.
The Exchange server does need to be directly exposed to the internet (Edge Transport or Hub Transport, that's your design choice) and this is typically done by NAT'ing ports (namely 25 for SMTP and 443 for OWA) on the router to the Exchange Server. The Exchange server also requires connectivity to Active Directory to function, but Active Directory doesn't need to be directly exposed to the internet to achieve this.
