A blockchain is a public ledger of all transactions that have taken place between parties. For the most part, every cryptocurrency is built on a blockchain, and is used as the medium of exchange, with cryptocurrency transactions being stored within each block on the chain. As a block is completed by the miners on a network, it is added to the chain of all blocks that have ever come before it. Users are able (in the case of most coins) to check at any time that their transactions have been verified by the network. Each computer connected to the network that is performing transaction verification (called a “node”) gets a copy of the blockchain, which is automatically downloaded when one joins a crypto network. The user is able to see all transactions and current balances from the most recently completed block all the way back to the first block, called the “genesis block”. On average, a new block is “mined” roughly every 10 minutes, and mining difficulty is designed to automatically adjust to maintain this rate.