Ethereum is one of the most popular public blockchains. It has its own cryptocurrency, called Ether (ETH) or Ethereum, and its own native programming language called Solidity to build and publish dApps (distributed applications) on the Ethereum blockchain.
Mainnet and Testnet
SettleMint supports both the Ethereum Mainnet and the Rinkeby Testnet.
The Mainnet is the primary public Ethereum production blockchain, where actual-value transactions take place. Each transaction requires payment of a transaction fee, payable in the native coin ETH. The Testnet is an instance of the blockchain to be used for testing and experimentation. There are also coins used in the Testnet but they have no value, so there is no risk of real fund.
You can consider the Testnet as a prototype and the Mainnet as the official production blockchain. Or think of this as an analog to production versus staging servers.
In order to participate in a blockchain, you need some form of client software that implements the features required to run a node. SettleMint uses Geth which is the official Ethereum client, written in the programming language Go, and fully open source. While there are other clients (like Parity), Geth can be seen as the de facto reference implementation for running an Ethereum node. It is the most widespread client with the biggest user base and variety of tooling for developers.
More information on Geth can be found on the official Geth website.
A consensus mechanism defines the rules for the nodes in a blockchain network to reach agreement on the current state of the blockchain ledger.
Ethereum runs on a Proof of Work (PoW) consensus mechanism. PoW gives a specific type of nodes, called miners, the power to validate transactions within the network and to create new blocks. The consensus mechanism is called Proof of Work because it requires the miners to perform some type of "work" – computer processing to solve a mathematical puzzle – for which they need to provide "proof" to the network. Once this proof of work is validated by the network, the blockchain is updated for everyone with the latest verified transactions, and the miner is rewarded for its work.
In the future, however, Ethereum plans to shift to a newer consensus mechanism called Proof of Stake (PoS).
More information on the consensus mechanism can be found on the official Ethereum website.