Currency refers to all the aspects of a nation's money supply and the forms it comes under, coins and banknotes.
There are online currency converters that are the most accurate but require Internet access to be used.
One can easily rely on desktop currency converters, regardless of the existence of any Internet connection, but they should be used for reference only, as their exchange rate is only approximated.
Currency converters require users to enter the amount, then select the source and the output currency (some of these applications support several output currencies for a single conversion).