The tractate deals with the details of many circumstances which could arise with regards to the terumah. Thus, for example, before the terumah is separated, all the produce is tevel (untithed) and forbidden to be eaten. Terumah is considered holy, and may be eaten by priests only, as prescribed  in Leviticus 22:10, and must be guarded against becoming ritually unclean, lost or wasted, as interpreted from Numbers 18:8.
The treatise addresses the intricacies of numerous situations that may occur concerning the terumah. For instance, prior to the separation of the terumah, all produce is considered untitled and forbidden to be consumed. The terumah is regarded as sacred, and can only be eaten by priests, as mandated in Leviticus 22:10, and must be shielded from becoming ritually impure, lost, or wasted, as interpreted from Numbers 18:8.