As we have learned, the sacrificial service is ordinarily limited by the Torah to a single, central location. When the Children of Israel were in the desert, sacrifices were brought only in the mishkan, the Tabernacle; once they settled in the Land of Israel they were limited to the mikdash, the Temple, in Jerusalem.
During the interim period between entering the Land of Israel and the erection of the Temple was a period of heter bamot– sacrifices were permitted on bamot ketanot, that is, on private altars. Nevertheless, during the time that the Tabernacle was standing in Shiloh (see daf 61) it served as a bamah gedola – a central place of sacrificial worship – and private altars were forbidden.
Some laws regarding sacrifices changed upon entering Israel. For example, the Torah introduces the laws of nesakhim – wine libations – with the words ki tavo’u el eretz moshvotakhem “when you come to the land of your habitations” (Bamidbar 15:2), indicating that it is only upon entering Israel that these laws will apply. Our Gemara quotes a baraita where we find a difference of opinion between Rabbi Yishmael who interprets that passage to mean that only when the people were settled and established the mishkan in Shiloh did the obligation of nesakhim begin, and Rabbi Akiva who understands that immediately upon entering the land all sacrifices required nesakhim.
The Gemara explains that this difference of opinion is based on a more basic argument between the tanna’im. According to Rabbi Yishmael, no nesakhim were brought in the mishkan in the desert, so the Torah had to teach this new requirement when the mishkan was established in Israel. Rabbi Akiva believes that nesakhim were brought in the mishkan, so the passage requiring them in Israel must teach about a new situation – that is, sacrifices brought on private altars, which were forbidden in the desert.