What is forward bias and reverse bias?

(N/A) Forward Bias: When the positive terminal of an external battery is connected to the $p$-type semiconductor and the negative terminal is connected to the $n$-type semiconductor of a $PN$ junction diode,it is said to be in forward bias. In this state,the depletion layer width decreases,and the potential barrier is lowered,allowing current to flow easily.
Reverse Bias: When the positive terminal of an external battery is connected to the $n$-type semiconductor and the negative terminal is connected to the $p$-type semiconductor of a $PN$ junction diode,it is said to be in reverse bias. In this state,the depletion layer width increases,and the potential barrier is raised,which opposes the flow of majority charge carriers,resulting in negligible current.