Megillah, Chapter 1, Mishnah 11. In the previous mishnah we learned that once the Mishkan was established in Shiloh, and likewise once the Beis HaMikdash was built in Jerusalem, it became forbidden to offer sacrifices on a bamah, and they could not be brought anywhere else. Our mishnah comes to distinguish between the laws of Shiloh and the laws of the Beis HaMikdash in Jerusalem.
"Ein bein Shiloh l'Yerushalayim ela sheb'Shiloh ochlim kodashim kalim u'maaser sheini b'chol haro'eh":
There is no difference between Shiloh, the site of the Mishkan, and the Beis HaMikdash in Jerusalem, except in one point: the place where kodashim kalim and maaser sheini may be eaten. Kodashim kalim are those offerings that need not be eaten specifically within the boundaries of the Azarah, and even those who are not kohanim may eat them, such as the shelamim offering. Maaser sheini, which is generally eaten only in Jerusalem, is included in this distinction as well.
In Shiloh: kodashim kalim and maaser sheini were eaten "b'chol haro'eh" - in any place from which one could see Shiloh, that is, the Mishkan.
In Jerusalem: they are eaten "lifnim min hachomah" - anywhere within the wall of Jerusalem.
It emerges that in Shiloh, which was not surrounded by a wall, it was enough that a person could see the Mishkan from where he stood; in Jerusalem, however, the permission depends on being inside the city wall.
"V'chen v'chen kodshei kodashim ne'echalim lifnim min hakla'im":
In Shiloh and in Jerusalem alike, kodshei kodashim - the highest level of offerings, eaten by kohanim alone - are eaten only within the kela'im. The kela'im are the hangings of the Mishkan, and in the Beis HaMikdash the reference is to the walls of the courtyard. There, and not outside of it, is the place where they are eaten.
"Kedushas Shiloh yesh achareha heter, u'kedushas Yerushalayim ein achareha heter":
The sanctity of Shiloh: as long as the Mishkan stood in Shiloh, it was impossible to offer sacrifices on a bamah anywhere else. But once Shiloh was destroyed, the bamos returned and became permitted, and during the years between the destruction of Shiloh and the building of the Beis HaMikdash it was permitted to offer sacrifices on a bamah.
The sanctity of Jerusalem: nothing is permitted afterward. Once the Beis HaMikdash was built, from that moment and forever, sacrifices can no longer be offered on a bamah, even after the Beis HaMikdash was destroyed.
For this reason we are unable to bring a sacrifice in our own day, until the Beis HaMikdash is rebuilt.
In summary: in this mishnah we learned two differences between Shiloh and Jerusalem: the place where kodashim kalim and maaser sheini are eaten - in Shiloh "b'chol haro'eh" and in Jerusalem "lifnim min hachomah" (while kodshei kodashim are eaten in both within the kela'im); and that after the sanctity of Shiloh a bamah was once again permitted, whereas the sanctity of Jerusalem is an eternal sanctity, and nothing is permitted after it.