Fork

Changing the blockchain code, as a result of which it starts working according to a different algorithm. During a fork, a continuous blockchain chain forks into two new ones, which start working independently of each other and according to different rules. After the fork, a new blockchain and a new coin appear.

Main types:
Soft fork - changing the rules does not require updating the client (software) to execute the new rules. If some of the nodes (nodes) in the network do not accept the new rules, such nodes will still be able to interact with the nodes that use the new rules.
Thus, a soft fork is a reversible code change that does not break the consensus on the protocol itself.

Hard fork - the new rules contradict the old ones so much that the nodes that did not accept them do not receive information from the nodes that accepted them. This type assumes a change in the very mechanism of consensus, in which case the entire network is divided into two parts that can never interact again. This is because blocks that are valid in one part will not be valid in the other.

The difference between a soft fork and a hard fork is easily explained by the analogy with languages. If before the soft fork the blockchain spoke British English, then after that it began to speak American. The two branches of the nodes will easily understand each other - just like the Americans and the British. And after a hard fork, the blockchain nodes do not switch to another dialect, but change the whole language (for example, to German instead of English), and do not understand each other.

What forks do you know, can you name examples?