What is 'depletion region' in a semiconductor diode?

The depletion region is

What is depletion region in p-n junction ?

What is meant by depletion region in a junction diode? How is this region formed?

What is meant by depletion region in a junction diode? How is this region formed?

What is depletion region in p-n junction diode. Explain its formation with the help of a suitable diagram.