I would like to ask how to explain several terms in stock index futures software trading: buy open position, sell open position, sell close position, buy close position, buy close position and sell close position. Buying a position: refers to buying more than one order when placing an order, that is, bullish and bullish index.

Selling and opening position: refers to buying an empty order when placing an order, that is, bearish or bearish index.

Buying and closing: refers to selling more than one order when placing an order.

Selling and closing: refers to selling the bought empty order when placing an order.

Buy flat today: refers to selling multiple orders bought on the same day when placing an order.

Selling flat today: refers to selling empty orders bought on the same day when placing an order.