(Fake in the context of this post is defined as Not Original / Not Genuine with reference to the Bitcoin Protocol.)
In 2009, the Bitcoin Protocol was released. It was called Bitcoin.
In 2017, a group of Core Developers introduced a change in the Bitcoin Protocol called SegWit (Segregated Witness) that was not part of the original design, destroyed the Incentive Based System of Bitcoin, and broke the Chain of Digital Signatures specified in the Bitcoin Whitepaper. It altered the Bitcoin design forever. Their coin is now represented by the symbol BTC and people call it Bitcoin Core (BTC).