the beginning the Prophet Satoshi brought us Bitcoin. And the cryptogeeks and libertarians looked upon it, and said lo, we smile upon this, for it is good, and decentralized, and solves the Byzantine Generals Problem. For a time all was well. But then came wailing and gnashing of teeth and wearing of sackcloth. And then came the Prophet Vitalik, bearing Ethereum; and lo, it was even better.Maybe.What is Ethereum? It’s a combination of a cryptocurrency, like Bitcoin, and a vast decentralized computer. Let me explain. As an above-average TechCrunch reader, you already know Bitcoin is a currency whose transactions are secured by the immense computing power of its distributed network of “miners,” rather than any central entity. But you may not appreciate that every Bitcoin transaction is actually a program written in the Bitcoin scripting language — aka a “smart contract.”Bitcoin’s contractual language is quite limited, by design. But it allows for transactions that can be delayed until a particular time; or transactions that occur only if, say, 3 of 5 signatories agree to them; or crowdfunding campaigns that only transfer money if a particular total is attained; and many other possibilities. Importantly, once incorporated into the Bitcoin blockchain, these contracts require no trust and no human intervention. Bitcoin is programmable money … with a highly restrictive programming language.Ethereum removes those restrictions entirely. The Ethereum scripting language is Turing-complete, meaning it can replicate any program written in any traditional programming language. However, to prevent ill-behaved contracts with infinite loops from running forever, every Ethereum transaction computation must be paid for. Just as Bitcoin miners collect small amounts of bitcoin, known as “fees,” in exchange for mining transactions onto the Bitcoin blockchain, Ethereum miners collect “ether,” the Ethereum currency, for running Ethereum contracts.You may well be thinking: “Oh come on. Bitcoin was more than abstruse and geeky enough. Now this new made-up-magical-money thing is even more complicated? Why should I care?”You should care because decentralized cryptocurrencies like Bitcoin and Ethereum are–or at least could be–essentially an Internet for money, securities, and other contractual transactions. Like the Internet, they are permissionless networks that anyone can join and use. Ethereum optimists might analogize Bitcoin as the FTP of this transactional Internet, with Ethereum as its World Wide Web.I’ve waxed about why I think Bitcoin matters. I’m a little less enthusiastic about Ethereum … so far. To be clear: as I’ve written before, Ethereum is really cool, truly innovative, and potentially revolutionary. However, it is now–probably–at the peak of its initial hype cycle.Consider: heavily funded Bitcoin startup Coinbase will soon support Ethereum trading on its rebranded cryptocurrency exchange. Microsoft offers “Ethereum Blockchain As A Service” on Azure. Ether has risen in value more than tenfold over the last year, to a market cap which now exceeds $1 billion. And while Bitcoin’s hashrate, a measure of the computing power devoted to mining, still vastly exceeds Ethereum’s, look at the hockey-stick nature of that latter chart.