Bitcoin is not only a cryptocurrency but also an open source software project that is available publicly to download and use. Bitcoin core is available on Github here: https://github.com/bitcoin/bitcoin.
It is not uncommon when the team of an open source project disagrees on some new features, changes, or updates. When a team splits and creates a separate branch of an open source software, it is called forking.
A fork that is compatible with the original code is called a soft fork and a fork that is incompatible with the original source code is called a hard fork.
Cryptocurrency projects such as Bitcoin, Ethereum, and others have several hard and soft forks.
Watch this video to learn more about Bitcoin hard fork.