Close a position refers to a trader buys or sells a contract with the same quantity and symbol but the opposite direction of the contract.

Close a position is divided into close on current market price and close in limit order 

Close a position on current market price refers to traders Buy/Sell at the current market price.

Close in limit order refers to traders setting an estimated price to close a position.

Close in pending order includes take profit and stop loss.

Take profit is a limit order. When the price fluctuates to a predetermined price, the profit reaches a certain level, the position will be closed automatically in time in your limit order. 

Stop loss means that when the price fluctuates to opposite direction, the loss of the holding order reaches a predetermined amount, the position will be closed in time to avoid larger loss. 

The purpose of stop loss is to limit the loss to a smaller range when investment errors occur. The stop loss is a limit order, when the price reaches your limit order, the stop loss order will be executed automatically.