E-currency is money that is exchanged on computers. "E" is the first letter of the word "electronic" and "currency" is a money system. You can think of e-currency as Internet money. Buying and selling products and services on the Internet is possible because of e-currency.
If it is Bitcoin or any cryptocurrency you sent, wait until it receives 1 confirmation in blockchain. If it is Perfect money or OKPAY, any payment can be hold by them for verification, so kindly wait until they release payment. Also in case you given wrong withdraw account details the payment can fail.