The noun מחנה (camp) refers to the people when they rested in a field and refers to Israel as long as they dwelt in the desert. And there is the whole camp and parts of the camp, since every tribe is called a מחנה. And after they established the Tabernacle, there were three camps – priests, Levites, and Israelites. And any place where it says מחוץ למחנה, it is explained according to its context.

And there is a difference between מחוץ לעיר (outside of the city) and מחוץ למחנה (outside of the camp): מחוץ למחנה is precisely in a place that is considered a מחנה according to Torah Law, for instance, Jerusalem or a walled city.