Is ERC-20 only on Ethereum?

Could you clarify something for me, please? I've been hearing a lot about ERC-20 tokens, and I'm trying to wrap my head around the concept. I've seen it mentioned in relation to Ethereum, but does that mean ERC-20 is exclusive to the Ethereum blockchain? Or is it possible for ERC-20 tokens to exist on other platforms as well? I'm just trying to understand the limitations and possibilities of this token standard. Your expertise in the field would be greatly appreciated.