Officially digital money or electronic is a representation, or a system of credits and debits, used (but not restricted to this) to swap value, within a different system, or itself as a separate system, offline or online. Also occasionally the expression electronic money is used to refer to the contributor itself. A personal currency may use gold to provide additional security, such as digital gold currency. An e-currency system may be completely backed by non-gold backed, gold (like e-gold and c-gold), or both gold and non-gold backed (like e-Bullion and Liberty Reserve). Also, some private organizations, such as the US military use private currencies such as Eagle Cash.
Many systems will trade their electronic currency straight to the end user, such as web money and PayPal, but other systems, such as e-gold, sell only through third party digital currency exchangers.
In the case of Octopus Card in Hong Kong, deposits work in the same way to banks'. Later than Octopus Card limited receives money for place from users, the money is deposited into banks, which is like to debit-card-issuing banks re-depositing money at central banks.
Some society currencies, like some LETS systems, work with electronic dealings. Cyclos Software allows formation of electronic community currencies.
Ripple monetary system is a project to extend a distributed system of electronic money self-governing of local currency.