You've Never Eaten ChallahBy Rabbi Jack Abramowitz
G-d also told Moshe that, after the Jews inherit the land, they were to give a gift (terumah) separated from their dough, the same way they do from their produce. This portion, called challah, was given to the kohein. Nowadays challah is still separated from dough, but it is burned. So you don’t eat challah on Shabbos, you eat bread from which challah has been taken.
If the community accidentally commits an act of idolatry (which is equivalent to all other sins combined) because they were misled by their leaders, they are to offer a bull as a burnt offering and a goat as a sin offering. They will be forgiven because they acted in error.