Entered Currency vs Accounted Currency

I have a ledger whose functional currency is in USD, the users are also entering a  Canadian Currency which forces the user to enter the type and rates.  Obviously, Oracle can support this type of process. My question is more on why are we allowing it?. It is because  so that the users will not do the conversion manually and have Oracle handle it for them?.  So when once approve, it is  the ACCOUNTED currency in US Dollar  gets posted  to the GL and the system is not doing anything on ENTERED currency in Canadian dollar?. It that correct? Are there