An order to execute a trade with indicated parameters is sent to a broker from the client terminal. The order correctness is checked on the server. Are all the parameters (balance, lot, price, etc.) indicated correctly? If any of parameters does not meet the requirements, the order is rejected. If everything is correct, a trade order is placed to the Order Queue, after which it is sent to a dealer or to the market. An order can be also rejected in the market (stock exchange) or by the dealer.
Trading operations Execution in MetaTrader 5An order turns into a trade if all its parameters are correct and it has been executed in the market. Depending on the current position for the security, the trade can result in the position increase, decrease or closing.
Example: we've got one position for EURUSD 1 Lot. If another lot is bought, the position will be increased to 2 lots. If 1 lot is sold, the position will be closed. If 0.7 lots are sold, the position will diminish to 0.3 lots.