in snow leopard it is as simple as adding the account to mail.
here's the basics:
outlook, is a microsoft office email client, which enables access to a proprietary email server setup (exchange). entourage is the mac equivalent, and while it shares quite a few features, it isn't as powerful as outlook is (microsoft being microsoft there). outlook enables you to use any of the standard variety of email server systems (POP, IMAP, HTTP, Exchange). alternately, outlook express functions similarly to outlook, but lacks some of the usability and exchange capacity.
mail, is apple's equivalent to outlook. it enables you to access emails over any of the standard server systems (POP, IMAP, HTTP, Exchange in 10.6/Mail 4).
in order to add an account to mail, you simply open mail, go to file, and add account. fill out the basic information, and it'll determine what type of account you have.
if it's an oddball, you may need some information about your email servers, but otherwise it's pretty straight forward