He's talking about a program that will retrieve your webmail and send it to your mail program on your computer. I've tried it and personally I don't like it at all, and Apple is smart in Mail, your server must be plus.mail.yahoo.com, so that blocks Mail, but I haven't tried it with Entourage, although I know you can change a lot of settings with it.
Why don't Yahoo users just switch over to Gmail, yah maybe you will have to notify people of a change, but what I have seen, is Gmail is a lot better and it provides POP.