Is Polygon Ethereum L2?

I'm curious to know if Polygon can be considered as an Ethereum Layer 2 solution. Can you explain what Layer 2 solutions are and how Polygon fits into this category, if at all? Are there any key differences between Polygon and other Layer 2 scaling solutions for Ethereum? I'm particularly interested in understanding the technical aspects of how Polygon operates and how it helps to address the scalability issues faced by the Ethereum network.