In order to scale Ethereum, the Layer 1 parent blockchain, Polygon was created as a Layer 2 blockchain. The development of Polygon aims to address scalability problems including slower transaction speeds and increased fees brought on by the success of Ethereum.
Instead of replacing or altering Eterheum, Polygon aims to make it a more effective and secure blockchain. Due to the proliferation of smart contracts and decentralized applications built on Ethereum, the platform has slowed down, and because transaction fees (also known as "gas fees") vary depending on network demand, they can get rather expensive.
The native cryptocurrency of Polygon, formerly known as the Matic Network, is called MATIC, and it is used to pay network transaction fees.