Why does buying an SSL Certificate have to be so hard and confusing?
Here is a link which (I hope) will make your selection of a SSL easier: https://www.digicert.com/ssl.htm
It’s actually fairly complicated stuff, and there is no real reason they don’t make it simpler; though most people who develop websites for a living know what it is, and what the various features offered mean. Not that that helps a person who isn’t a web developer.
