中文：

平仓和补仓是股票交易中常用的操作策略，它们的意思如下：

平仓：在股票交易中，平仓是指投资者在持有股票的情况下，选择以市价或限价的方式卖出股票，以获得收益或减少损失。平仓的目的在于锁定利润或减少亏损。

补仓：在股票交易中，补仓是指投资者在持有股票的情况下，在股票价格下跌时，选择以更高的价格买入股票以摊薄成本，以降低亏损或增加收益。补仓的目的在于降低风险或提高收益。

平仓和补仓的时机选择对于投资者来说非常重要。如果投资者能够准确预测股票价格的走势，那么平仓和补仓的时机选择就变得尤为重要。如果投资者预测股票价格会上涨，那么他们可以选择在价格上涨之前买入股票，然后在价格达到预期时卖出股票，以获得利润。如果投资者预测股票价格会下跌，那么他们可以选择在价格下跌之前卖出股票，然后在价格达到预期时买入股票，以减少损失。

总的来说，平仓和补仓是投资者在股票交易中常用的操作策略，它们的时机选择对于投资者的收益和风险控制都非常重要。

英文：

Closing and re-opening positions refer to commonly used trading strategies in stock trading, which are explained as follows:

Closing position: In stock trading, closing a position refers to investors selling stocks held by them at market price or limit price, in order to lock in profits or reduce losses. The purpose of closing a position is to lock in profits or reduce losses.

Re-opening positions: In stock trading, re-opening positions refers to investors buying more stocks at a higher price when the stock price falls, in order to dilute the cost and reduce losses or increase profits. The purpose of re-opening positions is to reduce risks or increase returns.

The timing of closing and re-opening positions is very important for investors. If investors can accurately predict the trend of stock prices, then the timing of closing and re-opening positions becomes particularly important. If investors predict that the stock price will rise, then they can choose to buy stocks before the price rises and sell them when the price reaches the expected level, in order to obtain profits. If investors predict that the stock price will fall, then they can choose to sell stocks before the price falls and buy them back when the price reaches the expected level, in order to reduce losses.

Overall, closing and re-opening positions are commonly used trading strategies by investors in stock trading, and their timing is very important for investors' returns and risk control.