The swap-free accounts are usually called Islamic, because initially these accounts were established for the traders following the Islamic religion. According to the religion's principles, any business transactions, where one of the parties should pay or get an interest from the other one, are prohibited. Islamic or swap-free accounts allow traders to trade any currency pair, but despite the volume of a trade, which is carried over midnight, do not suppose any reward or withdrawal.
The accounts, which do not have the swap influence, give its owners an opportunity to keep the positions opened during an indefinite long period and do not provide any negative or positive commission for the rollover. In this case, the result of trading depends only on currency rate's movement for that certain period. Thanks to its peculiarity, this type of accounts became popular not just in Islamic countries, but also in other countries all over the world.
InstaForex, as well as many others Forex brokers, offers its clients the swap-free accounts for free.