One big difference to Forex are the big spreads. A spread is the difference between ask and bid prices. The ask price is the highest price that someone wants for a given cryptocurrency, this is essentially the buying price. The bid price is the lowest price someone is willing to give you for a given cryptocurrency, this is basically the selling price.
In 1998, Wei Dai published a description of "b-money", characterized as an anonymous, distributed electronic cash system. Shortly thereafter, Nick Szabo described bit gold. Like bitcoin and other cryptocurrencies that would follow it, bit gold (not to be confused with the later gold-based exchange, BitGold) was described as an electronic currency system which required users to complete a proof of work function with solutions being cryptographically put together and published. A currency system based on a reusable proof of work was later created by Hal Finney who followed the work of Dai and Szabo.