Currency deposited by national governments or corporations in banks outside their home market. This applies to any currency and to banks in any country. For example, South Korean won deposited at a bank in South Africa, is considered euro currency.
One advantage of euro currency
from a bank's point of view is that it allows a bank
to
operate outside the regulation of the country issuing
the currency in question.
One
particular advantage is that most countries do impose a reserve requirement
on foreign currency operations: a bank can therefore lend a higher proportion of its
euro currency deposits, improving its interest margin.