I sit and look at the SSL certificates and web host.
Direct what is the difference between a shared SSL certificate and other SSL certificates?
A "shared SSL certificate" isn't a special type of certificate. It's just a standard SSL certificate that is shared between different people/organizations. In theory this would be bad practice, but the public key infrastructure of SSL is so corrupt that in reality it doesn't really matter (except to the CAs, of course, who would prefer that everyone bought their own certificates).
Usually it just means the web host has a wildcard certificate that they share with all their customers, e.g.
htps://user1.example.com htps://user2.example.com htps://user3.example.com
Or they host everyone's secure pages under a single domain, e.g.:
https://secure.example.com/~user1 https://secure.example.com/~user2 https://secure.example.com/~user3
It's a cheap way to use a CA-signed certificate if you dont't mind the URL limitations.