As of March 2018, there were a total of three Ethereum ATMs in operation worldwide. Two of these were located in the United States, and the other was in Canada.
As Ethereum becomes more popular, it is likely that the number of ATMs will grow.
Ethereum is a decentralized platform that runs smart contracts: applications that run exactly as programmed without any possibility of fraud or third party interference. These apps run on a custom built blockchain, an enormously powerful shared global infrastructure that can move value around and represent ownership of property.
This enables developers to create markets, store registries of debts or promises, move funds in accordance with instructions given long in the past (like a will or a futures contract) and many other things that have not been invented yet, all without a middleman or counterparty risk.
The Ethereum network is kept running by computers all over the world. In order to reward the computational costs of both processing the contracts and securing the network, there is a reward that goes to the computer that solved the most recent problem. Every 12-15 seconds, on average, a new block including between 2 and 5 transactions is mined by one computer on the network. The winner gets 2 ETH + all the transaction fees included in their block (usually 0.
00001 to 0.001 ETH). They also get to keep any extra data they want to include in their block as long as it doesn’t violate some arbitrary size limit.