What’s the relationship between Polygon and Ethereum?

I'm not shilling Polygon. I just would like to understand what it means that Polygon is the "internet of blockchains" and what that means longterm in relation to ETH. I understand it's an L2 scaling solution but there are many of those out there right now. What interests me is that it builds ETH compatible blockchains. Is that what makes it more valuable? Where do you think Polygons importance is long term practically speaking?