Bitcoin Cash (BCH) forked from Bitcoin on August 1, 2017 as a result of a consensus dispute over the path to scalability. While Bitcoin (BTC) devs insisted on keeping block size small and scaling using Layer 2 solutions such as Lightning Network, the proponents of Bitcoin Cash wanted to scale by increasing the block size and allowing more transactions to fit in each block.
Each method has its pros and cons, and both have coexisted as market participants continue to speculate and support both blockchains concurrently.
Bitcoin Cash is a fork of Bitcoin and shares the same UTXO blockchain model. It is an altcoin to Bitcoin.