The currency converter simply translates a value from one currency to another. For example, it shows you the current equivalent of $10,000 in EUR.
The calculator uses live prices, and will update on each market tick. Depending on which currencies are selected, the calculator may either be able to do a direct conversion (e.g. between USD and EUR using EUR/USD), or it may need to triangulate via the US dollar (e.g. converting CAD to GBP by using USD/CAD and GBP/USD).