Account vs. Application vs. Network confusion

OK, I just installed WLM for the first time, and am able to chat with
friends associated with my Facebook account. Facebook even has its own
category in WLM. However, I am having trouble communicating with
people who have hotmail accounts.

How do I communicate with them?
Do I need to sign up with hotmail to chat with them?
My Windows Live account is associated with my GMail account. Is that
going to pose a problem?

I'm thoroughly confused as to the difference between my Windows Live
account, the different networks WLM reports people as belonging to,
and what it is I need to sign up with to talk to who.

Any help would be graciously appreciated.


-MH