Nagaraju,
For the people who cannot trade during Market hours, AMO orders facilitate them to Place the order after market hours. This is a added facility provided by the brokers to their client.People who can’t actively track the markets from 9:15 AM to 3:30 PM. You can place orders any time from 6:30 PM to 9:15 AM (until just before market opening). So you could plan your trades and place your orders before the market opens. After-market orders can be placed on all the exchange segments. Please note that if you place any after-market order between 9:15 AM and 6:30 PM, they could all be cancelled by 6:30 PM. AMO is allowed only between 6:30 PM and 9:15 AM. Another important thing to remember with AMO is that between 8:45 AM and 9:15 AM you cannot modify or cancel any orders that are already placed.
For Commodity : After-market orders for commodity can be placed after closing of the commodity markets till 10:00 AM (MCX opening).
Regarding Execution of AMO orders : As soon as the market opens at 9.15am, all the AMO orders are sent by the broker end to Exchange.