Question: I’m going to be in Chicago for 5 days in a couple of weeks, and A Chicago beef sandwich is most definitely on my "to eat" list thanks to learning of them on this site.

That said, I see the "Chicago Beef sandwich" talked about but also the "Italian Beef".

1) Are these two terms interchangeable?
1a) if not, can someone tell me about the differences?
2) Suggestions other than Mr Beef (which I intend to stop at) as the place to go to get these sandwiches? Keep in mind that this will be a "first time" experience for me, but that I am comfortable walking/bussing/subwaying to whereever within reason

I think I will hit Lou Malnatis and the Billy Goat Tavern for two other Chicago experiences — I’m not big on Hot Dogs/Sausages