Is ERC-20 the same as Ethereum mainnet?

Excuse me, I've been hearing a lot about ERC-20 and Ethereum mainnet, but I'm still a bit confused about the relationship between them. Could you clarify for me? Are ERC-20 tokens and the Ethereum mainnet essentially the same thing? Or do they have distinct roles and functions within the cryptocurrency and finance landscape? If they're different, what exactly is the difference? And how do they interact with each other? Your insights would be greatly appreciated!