Can someone help me understand them better and how they work.
I am familiar with IIS, but never work with SSL.
I have a ded. box running 3 websites, via 1 IP using Host headers. Each of the three need SSL Cert now. Someone said each would need a static IP, is that true. I only have 5 IP's ow do I make this work?
Yes, you will need a different IP address for each of your SSL sites. https does not switch based on the Host: HTTP header like http does.
If you've already got name based virtual hosting working for your three current sites you're well on your way. If you need SSL/https for all three then you can keep the non-SSL sites on name based virtual hosting and have the SSL sites each on their own IP. You'll still have one IP left over.
I'd search WHT for information on the best provider for SSL certificates. There are many and there are pros and cons of each.