If you have a finished basement, it may be hard to tell the difference between a poured concrete or stone foundation. But, it's usually not hard to tell at all. Look in the basement; if you see stones you have a stone foundation, if you see smooth cement walls you have poured concrete.
It becomes tricky when people do renovations or rehabs on a house. They'll put in a layer of mortar over the stones to make it smooth so it looks like a poured concrete foundation. That is where you have to be careful.
There is a way you can tell. You have to poke around a little bit. If there are some loose areas poke in there and remove a little bit of mortar and see. Or, you can tap on it with your knuckle or lightly with a hammer; if you hear hollow sounds you can pretty much be sure that it is mortar that has been put on top of a stone foundation. This is done on the inside and sometimes on the outside as well.