Bitcoin Core is Bitcoin — that’s right, it’s the original BTC.
More specifically, it’s the software that runs the Bitcoin network. It was formerly called Bitcoin-QT.
Bitcoin is also known as Bitcoin Legacy because of forks.
Three of the more popular, non-compatible forked versions of the original Bitcoin Core software are Bitcoin Gold (BTG), Bitcoin SV (BSV), and Bitcoin Cash (BCH).
In layman’s terms, forking software means copying it and taking it in a different direction.
If you’d like to be a node on the Bitcoin network, or even mine Bitcoin, visit the Bitcoin Core website to download the latest software.
Unfortunately, due to the high global Bitcoin mining hashrate — its computational power, you’ll need dedicated hardware known as application specific integrated circuits (ASICs) and to join a mining pool to make mining profitable. One place from which you can buy ASICs is Bitmain, but due to high demand, they’re expensive.