encryption in ssl profiles

I have a question.... in the case where both client and server ssl profiles are enabled, do we need a certificate in the server ssl profile? how does encryption/decryption happen in the following scenarios?

1- there is no certificate in server ssl profile, there is certificate on the server 2 - there is certificate in server ssl profile, there is certificate on the server, both the certificates are same 3 - there is certificate in server ssl profile, there is certificate on the server, both certificates are different.