Is ERC20 the same as ETH?

I've been hearing about ERC20 tokens a lot in the cryptocurrency world, and I've also encountered ETH quite frequently. However, I'm still a bit confused as to whether ERC20 and ETH are interchangeable or if they serve different purposes. Could you please clarify the difference between them for me? I'm aware that ETH is the native token of the Ethereum blockchain, but does that mean all ERC20 tokens are also ETH? Or are they separate entities with distinct functions within the Ethereum ecosystem? It would be great if you could explain this in a way that's easy to understand for someone who's still learning the ropes of crypto.