This means that the Bitcoin network has been "cloned", so any user who had Bitcoin at the time of the fork (August 1, 2017) acquired Bitcoin Cash equivalent to the amount of BTC held (the wallet used had to support the hard fork).
The question may arise, what is the difference between the two cryptocurrencies?
The cryptocurrency world has been arguing for years what exactly would be the best way to extend Bitcoin to multiple users. The most popular solution was the larger block size introduced by BCH. So, Bitcoin's 1-megabyte block limit has been increased to 8 MB for Bitcoin Cash, due to this protocol more transactions are available at a lower cost and in less time.