Terumah (or Terumat HaMaaser) and ma'aser are tithes taken from produce grown in Israel. These kinds of tithes used to go for use in the Temple. However, since there is no place for the tithes to appropriately go, the tithe amount (about 1%) is set aside and discarded. The main thing seems to be that this 1% that was for Temple use should, at least, not be used mundanely.
08 July 2008
Kosher Fruit, part 2
The very helpful "Web(be) Rebbe at OU says, "When the OU certifies fresh fruit as Kosher, the OU makes certain that the fruit is not infested with insects (with the exception of unopened figs and dates) and that it does not come from Israel or if it the fruit is imported from Israel, that terumah and ma’aser has been taken from the fruit."