You may have heard about the recent Bitcoin Cash hard fork. This is a great opportunity to explain what exactly a hard fork is and why they happen.
In essence, imagine if your favorite video game or phone app enforced all users to upgrade their software in order to play or use the app. The way a hard fork operates is similar this premise. Hard forks upgrade the network protocol which doesn’t allow older versions of software to continue to the network. This creates a permanent split or fork from the prior state of the blockchain.
Upon the addition of a new feature or new code, the fork is initiated allowing for a new blockchain and a continuation of the old chain. Usually, users of the crypto-currency will adapt to these changes by upgrading their software in support of the new changes. Miners or node-operators who do not upgrade will not support the new chain and there create a permanent divergence of the two different chains.