Expert Advisors are incredibly valuable tools that, when used correctly, allow you to independently handle various aspects of trading in the financial markets. To put it more specifically, an Expert Advisor is similar to a robot that manages the positions of investors participating in online trading: all of this happens automatically. Essentially, Expert Advisors have the ability to open and close a position for any asset type. This is also what is known as automated or algorithmic trading. Practically speaking, these are files with an EX4 or MQ4 extension and operate based on If and Then strings.
The MQ4 file extension is Metatrader Custom Indicator File, designed and developed by MetaQuotes Software Corp. MQ4 file format. MQL4 is short for MetaQuotes Language 4, which is the language used to program Expert Advisors.
Through the MetaTrader 4 and MT5 MetaEditor settings, anyone can write their own indicator and program it to independently define their trading strategy. To access this setting, simply go to Tools and then click on the MetaQuotes Language Editor; alternatively, simply click on the MetaEditor icon in the toolbar.