SQL Server Agent Alert System - Operators?

[aj]

SQL Server 2005 SP2 64-bit

I am quite confused about the SQL Server Agent Alert System.

I have configured Database Mail, establishing my Profile(s) and
Account(s), and specifying SMTP server+port. I then configured SQL
Server Agent, under Properties->Alert System, to use Database Mail,
specifying a particular Mail Profile to use.

I then go into the properties of one of my Agent Jobs, and under
Notifications, expect to see, perhaps by default, the Database Mail
profile I picked when configuring Agent, or perhaps an account under
that particular profile.
Instead I have to pick an Operator. What do Operators have to do w/
the accounts/profiles in Database Mail? Shouldn't Database Mail have
made Operators unnecessary and obsolete?

When I define an Operator, I only specify an e-mail address, not an SMTP
server or port. How does it know the server/port to use? Does it
use those defined under Database Mail? If so, what account?

Can someone explain this to me?

thanks

aj