Some PI Doubts

Hi Experts,

Could you please throw some light on following:

How do we execute a Proxy scenario and what and all the steps will take to test the proxy?

Correlation: I need a exact definition for correlation: I searched the sdn but I couldn't.

Message Control in IDoc??

What should be the answer for the question: What is landscape of your client??

Routing Rules??

Difference b/w HTTP and HTTPS?

What is registered server program??

Thanks in advance...

Ramesh.