Sometimes referred to as an iceberg order, a reserve order is a form of limit order where you can set the display quantity which is the quantity that can be seen on the order book.
For example: If you placed a buy limit order for 0.02 BTC with limit price of PHP 1,000,000 and display quantity of 0.01 BTC, your order will reflect on the order book as 0.01 BTC at the price of PHP 1,000,000 and will be fulfilled once the system finds an EXACT match for an order selling BTC at PHP 1,000,000.