Closing Session of Market !

Dear all Could u plz tell me why there is a closing session in the market after regular market ?

To correct any error in trade, etc. Ex: You may mistakenly sell some shares which you don't have, you can try to cover them here.

I am not sure of this, but I think only market orders are allowed here, limit orders are rejected here. The market price is the 'close' price and all buying/selling should be done at that price only.

thnx a lot for reply sir