The Original Breach Time is end time of SLA calculated when it is attached on a task. During the course of SLA, the task might be moved to pending, which can pause the SLA. When the SLA is paused, the time saved is not included in the original breach time as it was calculated initially.
The Planned End Time on the other hand adds the pause duration to the original breach time, returning the actual end time adjusted for one of the following:
Documentation topic: Task SLA table