Orders are trade requests accepted by the trade server. If the request is invalid, it will be rejected. There are 2 types of orders: market and pending orders
Market orders represent instructions to sell or buy a certain amount of a specified financial instrument at the current market price.
Pending orders represent instructions to execute the trade subject to certain conditions. Pending orders have a certain expiration time upon which they are deleted.
Trades represent the results of the execution of orders (instructions to execute a trade). Every trade is based on a certain single order, whereas a single order can result in multiple trades. For example, an order to buy 10 lots can be executed by a partial execution of a number of consecutive trades. Trades are always stored in the trade history and cannot be modified. The terminal displays trades in the "History" tab.
Positions represent the outcome of orders in action. Only one position, either Long or Short, can be opened for each single symbol.
Stop Loss and Take Profit are special orders placed as a "fallback measure". I.e. in case of mistakes or a position opened by the Expert Advisor that is showing a loss, a Stop Loss order can limit losses at a certain predefined level. Take Profit acts in a similar way, only limiting profit in this case. It may become necessary to stop worrying about closing a position. It will get closed upon reaching a certain price level. In other words, these orders represent our "insurance plan", should the market turn against us or should we want to take profit. This type of orders cannot be placed separately on its own - it can only modify already existing positions.