In a centralized system, to perform software upgrades, you simply need to click on “Upgrade” in the app store.
However, in a decentralized blockchain system, upgrading is not an easy task and might even create a blockchain fork due to disagreements.
In short, A fork occurs when disagreements arise when the blockchain undergoes upgrades. As there is no central authority, To upgrade the decentralized protocol, the entire Bitcoin community needs to approve it. If there are any disagreements, A fork will occur.
Take Bitcoin as an example.
July 2017, to solve the Bitcoin’s network congestion problem, some bitcoin enthusiasts proposed Bitcoin Cash as a solution, resulting in the fork of the Bitcoin blockchain. Depending on the compatibility with the existing blockchain, a fork can be classified as a “hard fork” or “soft fork”.