What does a fast recovery diode mean?

Fast recovery diode:
Can be understood as fast diodes, high-frequency diodes, usually used in switching power supplies as rectifier diodes, inverter circuits as continuous current, reverse voltage absorption diodes.
The diode is a single PN junction semiconductor device, which has the characteristic of unidirectional conduction. It turns on when the forward voltage is applied and shuts off when the reverse voltage is applied. When the voltage reverses, the transition of the diode from forward conduction to reverse cut-off state takes a period of time to complete, which is called reverse recovery time.
The reverse recovery time varies according to the chip process, which is usually divided into four categories:
1. Ordinary rectifier diode, reverse recovery time is longer than 500nS (nanosecond).
2. Fast recovery rectifier diode, reverse recovery time 150-500nS (nanosecond).
3. High efficiency rectifier diode, reverse recovery time 50-100nS (nanosecond).
4. Ultra-fast rectifier diode, reverse recovery time 15-35nS (nanosecond).
5. Schottky rectifier diode, which has no reverse recovery time in theory, is actually less than 10nS (nanosecond)