"Electronic money is defined as monetary value which is:
* stored on an electronic device; * issued on receipt of funds; and * accepted as a means of payment by persons other than the issuer.
Working e-money examples: PayPal and MoneyBookers." (http://events.ccc.de/congress/2011/Fahrplan/events/4668.en.html)
From the Wikipedia:
"Electronic money (also known as e-currency, e-money, electronic cash, electronic currency, digital money, digital cash, digital currency, cyber currency) refers to money or scrip which is only exchanged electronically. Typically, this involves the use of computer networks, the internet and digital stored value systems. Electronic Funds Transfer (EFT), direct deposit, digital gold currency and virtual currency are all examples of electronic money. Also, it is a collective term for financial cryptography and technologies enabling it.
While electronic money has been an interesting problem for cryptography (see for example the work of David Chaum and Markus Jakobsson), to date, the use of e-money has been relatively low-scale. One rare success has been Hong Kong's Octopus card system, which started as a transit payment system and has grown into a widely used electronic money system. London Transport's Oyster card system remains essentially a contactless pre-paid travelcard. Two other cities have implemented functioning electronic money systems. Very similar to Hong Kong's Octopus card, Singapore has an electronic money program for its public transportation system (commuter trains, bus, etc.), based on the same type of (FeliCa) system. The Netherlands has also implemented a nationwide electronic money system known as Chipknip for general purpose, as well as OV-Chipkaart for transit fare collection. In Belgium, a payment service company, Proton, owned by 60 Belgian banks issuing stored value cards, was developed in 1995.
A number of electronic money systems use contactless payment transfer in order to facilitate easy payment and give the payee more confidence in not letting go of their electronic wallet during the transaction." (http://en.wikipedia.org/wiki/Electronic_money)