A cheesteak consists of:
- Rib-eye steak -- sliced very thin or chopped
- Cheese: Provolone, American, Whiz, and perhaps Mozzerella (exercise caution).
- Toppings: fried onions (obtained by merely saying "with" or "wid" in local parlance), green peppers (optional), mushrooms (optional), red sauce (but then it's a pizza steak, which is almost it's own entity, so tread carefully).
If you have something before you that has any component not mentioned above IT IS NOT A CHEESESTEAK. It may be a "steak and cheese." It may be a sandwich or sub of some kind. But it ain't no cheesesteak. And even if it has the above components but has been obtained anywhere more than 50 miles outside of Philly proper, it still debatable as to whether it is in fact a cheesesteak. Consult a professional if there's any doubt by dialing 215 and seven numbers of your choosing. You should be able to obtain knowledgable guidance.