Rationale behind Business Partners

Hi,

I am trying to configure Support Desk functionality of Solution Manager. There were 2 things which i needed to ask :

1) What are actually Business Partners? In case all my users are internal then what Business Partner signifies?

2) Secondly i wanted to ask about the rationale behind Sales Organization Data. Again here as well i need to ask if all users are internal then what data must exist there?

Also if anyone has configured Support Desk would you please also let me know that, does the above mentioned details are suppose to be entered by message processor or these details are incorporated within the message when a users posts a message to Support Desk from a satellite system.

Thanks,

Bilal Nazir