Polygon and ETH

So I just downloaded Coinbase and Coinbase wallet. And transferred $5.49. To test it. But that isn’t my question. So because of fees and gas and those types of things. I am bridgeing it to polygon (my ETH) but…. For NFTs… can I still buy ETH NFTs with Polygon. Or do I need to transfer it to ETH??? Or should I just keep it ETH? It may sound confusing but all I’m wondering is: can polygon be used for Ethereum purchases, for example NFTs