Bitcoin Cash is a hard fork of bitcoin. Members of the bitcoin community have long disagreed about the future of bitcoin on the issue of the scalability. The majority of the community had agreed on implementing a function called segwit2x that would increase the block size from 2mb to up to 8mb. SegWit2x makes the amount of data that needs to be verified in each block smaller, by removing signature data from the block of data that needs to be processed in each transaction, and having it attached in an extended block. So multiple transactions are verified at once instead of each transaction. This would presumably decrease transaction times making the protocol scalable. However, many developers were concerned that this would not address the issue of slow transaction times. So, in August 2017, some members hard forked a new currency called bitcoin cash. The bitcoin cash fork increased the block size to 32mb. The larger block size decreases the cost of validating a transaction on the network, making it more scalable as a medium of exchange for everyday transactions. They also added new opcodes to allow for effective smart contracts.
The new currency includes the same amount of coins that are on the bitcoin network. So, there are the same number of bitcoin cash coins as there are bitcoins. Since then, bitcoin cash has seen wide adoption.