During Market Hours:
When the stock market is open (9:15 AM to 3:30 PM on weekdays), we immediately send your buy or sell order to the exchange once you place it. Your order is then matched and executed at the best available price, depending on whether it's a market or limit order.
After Market Hours:
If you place an order after 3:30 PM, when the stock market is closed, it cannot be sent to the exchange immediately. We hold your order until the market opens the next day at 9:15 AM, after which it will be processed like any other order placed during market hours.