A Bitcoin Hard Fork is a software update that adds software improvements and many other changes to the Bitcoin network. When a Bitcoin hardfork happens, all clients mining bitcoin need to update the software.
If some clients continue to use the previous client, then there will be chain split of the bitcoin network and this will result in two different chains. This is why all, I mean 100% of the clients need to agree to a upgrade or there is a risk of chain splitting.
If chain split occurs, then there will be two different currencies. The chain with the highest consensus will be most likely recognized as Bitcoin and another chain will have another name.
When Ethereum hard forked after the DAO hack, there was two currencies that resulted in that hard fork. Ethereum and Ethereum Classic.
Hard Fork is a condition when a cryptocurrency developer team agrees to apply new features or changes to the coin programming system. Usually this is done to secure a cryptocurrency network or adapt to the growing number of coin users. Hard Fork can cause a mismatch between the old version and the new version, so all cryptocurrency users need to update all applications related to the coin in order to keep doing the transaction properly.
Bitcoin Hard Fork
Bitcoin is growing and developing rapidly as it is now because it is supported by its loyal community. This Bitcoin community consists of users, exchange platform (market), wallet (wallet) service platform, business, developer, and miner (miner). Along with the trend of using Bitcoin which is increasingly popular, now Bitcoin can only process certain amounts of transactions due to the limited block size. This caused Bitcoin transactions to enter and exit to be slow and more expensive than a few years before. This is what is being debated by the relevant communities so as to bring up the idea for Hard Fork.
What is Bitcoin Hard Fork and What Should I Do
Bitcoin is an open source financial technology through mutual agreement in its formation. Anyone has the right to submit changes and improvements to Bitcoin technology. Bitcoin miners are allowed to vote and implement these changes, and Bitcoin users can decide to follow these changes or not.
If the proposed changes are significant, the new version of the technology (in this case the new version of Bitcoin) will be created. This new version might not match the old version. If the Bitcoin community feels this change is controversial, the new version will fork from the main branch (old version) and operate with new rules (new version). In other words, these two technologies will go their own way, just as Bitcoin has given birth to Bitcoin Cash. "Because the fork process is too hard, then finally Bitcoin breaks into two".
Hard Fork is a considerable update (change) that must be made to a system, especially in crypto currencies. Bitcoin Hard Fork means that this system changes in the scope of the Core Bitcoin (Bitcoin Classic) system. Usually, Hard Fork is only done if the node in the Core Bitcoin network cannot validate a new, valid block, because there is a difference between the nodes that have used the new Core Bitcoin consensus protocol, and the old ones.
The consensus difference occurs permanently, whereas in every new block on bitcoin that the miner must validate there are hundreds to thousands of transactions. This becomes very dangerous, and the only way to go is with a Hard Fork.