Basically, Bitcoin Core is a Software that runs on the Bitcoin Network and was released by the Bitcoin Community itself and includes a wallet that can be used to store and send bitcoins. Also, Bitcoin Core is used to mine bitcoins. The name Bitcoin Core also serves to indicate that this is software directly descended from the original Bitcoin and to differentiate it from the so-called hard forks of the network: Bitcoin Cash, Bitcoin Gold, Bitcoin Diamond2.
As many people know, Bitcoin Cash, for example, emerged as a "variant" of the original bitcoin to focus 100% on exchanges and payments - given that the bitcoin network is more expensive - as it values security and decentralization , but BTC Cash has not seen the same success.
Bitcoin Core was developed by Wladimir van der Laan based on the original reference code by Satoshi Nakamoto. It is worth remembering that BTC Core is Open Source and anyone can propose improvements to the base code, and it will be evaluated by the community - and if possible, implemented.