What is depletion region in PN junction?

when the p type semi conductor is connected to n type the electrons in n type migrates towards p type to fill the vacancy i.e holes in p type. As a result accepter ions are developed in n type and donor ions in p type which restrict further movement of electrons and holes . this layer of donor and accepter ions at the pn-junction is called depletion region. and across this region a potential is developed which is called barrier potential.