Parameters from Price Charts and Trading Rules
First of all, we must consider the principles or rules used by the brokerage firm to form the price of a security or a pair. This principle consists of a broker offering two-way quotes of trading to conduct trading executions.
The two-way quotation is a pair of market price offered by the broker to buy and sell the asset for (symbol) pair at the moment.
BID is the lower of the two market prices offered by the broker in a two-way quote for a pair.
ASK is the higher of the two prices offered by the broker in two-way quotes for a pair.
Point is the unit of price measurement for symbols (minimum price changes that may occur, the last significant number of the price value).
Spread is the difference between a larger and smaller price in points in a two-way quote for a symbol.
Typically, spreads are fixed values. In MetaTrader 4, usually displayed in the chart window of a (symbol) pair only reflects the change in Bid price, but can also display the Ask price.
The picture above shows us a chart window of a pair where we can see BID price changes and two-way quotes – the current BID price line (black, 1.22209) and the current ASK price line (red, 1.22221). It can easily be seen that, in this case, the broker offers 1.2 points spread. Historical data for ASK pricing is not shown in the graph, but is implied and can be easily calculated for any time.
After knowing the parameters in the price chart, then note that the general trading rules from the trader side is, if the trader wants to buy the trader will get the price of ASK as the purchase price. Then, if the trader wants to sell then the trader will get the BID price as the selling price.