What Is Fork?
Fork is a a product launched based on the open source code of another existing product. Often forks are also called clones.
In the context of on-chain forks, forks usually are hostile to the original project and competes from the same users. Forks often do not innovate, or make the product technically better.
Unlike traditional open source projects, fork rarely co-operate. Because many forks lack the same technical understanding as the original founding tech team, forks suffer from hacks and are often abandon after a short period of time.
Forks in practice:
Blockchains can be forked. The most forked blockchain is Ethereum and its EVM architecture. Ethereum forks include Polygon, BNB Smart Chain, Avalanche C-Chain, Fantom.