Bitcoin Cash (BCC or BCH) is a hard fork of the original Bitcoin blockchain with upgraded consensus rules to allow scaling. It is a peer-to-peer, fully decentralized cryptocurrency, different from bitcoin but sharing the same past. As in the Bitcoin network, Bitcoin Cash has no central bank and requires no trusted third parties to operate.
The legacy Bitcoin (BTC) had a maximum limit of 1MB of data per block, or about 3 transactions per second. Because the community could not reach a consensus to raise that limit, the Bitcoin Cash was born as a hard fork of the Bitcoin's ledger at block 478,558 on August 1st, 2017. It immediately raised the block size limit to 8MB as part of a massive on-chain scaling approach.
Anyone who held Bitcoin as of block 478558 (August 1st, 2017 about 13:16 UTC) have the same amount of Bitcoin Cash as they had Bitcoin at that time.
Any transactions after the August 1st hard fork are completely separate between Bitcoin and Bitcoin Cash. This means any Bitcoin acquired after the split does not include any Bitcoin Cash, and any Bitcoin Cash does not include any Bitcoin.
Bitcoin Cash implements strong transaction replay protection. Transactions use a new signature hashing algorithm indicated by the flag SIGHASH_FORKID. These signatures are not valid on the Bitcoin Legacy network. This prevents Bitcoin Cash transactions from being replayed on the Bitcoin blockchain and vice versa.