i dont understand this....

 

when to use ?

what to use ?

and which to use ??

 

 

 
You should also read this :
Documentation on MQL5: Standard Constants, Enumerations and Structures / Environment State / Symbol Properties
Documentation on MQL5: Standard Constants, Enumerations and Structures / Environment State / Symbol Properties
  • www.mql5.com
Standard Constants, Enumerations and Structures / Environment State / Symbol Properties - Reference on algorithmic/automated trading language for MetaTrader 5