The triple bar has many meanings depending on the context where it is used. The equal symbol should be differentiated from other symbols which have the same shape.
In mathematics, it refers to an operation where the value of the operation is true when each side of the argument has the same value. In philosophy, it was used to argue that two statements can be identical if only one statement can substitute the other without any change in the meaning.
In logic, it means ( if and only if ), it is also called material equivalence. It is used for the metalogical notion of logical equivalence.