App note from Vishay which focuses on the diode’s losses present during the forward and reverse condition. Link here (PDF)
In the forward condition, diodes carry the current while showing the lowest resistance at the current flow (ON state) and the lowest possible voltage anode to cathode. In the reverse condition, the voltage anode to cathode across the diode is negative (OFF state) and the device is like an open circuit; the current flowing through the diode the leakage current is very small.
The transition between the forward and reverse conditions is called recovery. Forward recovery is when a diode goes from the OFF state to the ON state. Reverse recovery is when a diode goes from the ON state to the OFF state. These transitions are associated with losses, known as switching losses. Usually, forward recovery losses are negligible; but reverse recovery losses particularly those in high frequency circuits can be a non-negligible portion of losses present in the diode.