Hard fork
A hard fork is a major software update that creates a new version of a blockchain network that is not compatible with previous versions. This results in a permanent split in the network, creating two separate blockchains with identical transaction histories up until the fork.
Hard forks are implemented for various reasons, such as updating the network with new features and improvements, fixing security vulnerabilities, or resolving disagreements over the direction of the network. Hard forks require the consensus of a majority of network participants to become effective.
Hard forks can be contentious and can lead to a split in the community, as some may choose to continue using the old version while others move to the new version. This can result in a new cryptocurrency being created, as was the case with the hard fork that created Bitcoin Cash from the original Bitcoin network.