How much is 1 core to BTC?

Could you please clarify for me, how much does one core correspond to in terms of Bitcoin? I'm trying to understand the relationship between these two units and it's a bit confusing. Is there a fixed conversion rate or does it vary based on certain factors? Could you break it down for me in a simple way? I'm still new to the cryptocurrency world and I'm eager to learn more about it. Your explanation would be greatly appreciated. Thank you in advance for your help!