Polygon/MATIC is an integration that provides scalable, secure and instant transactions on Ethereum.
You can read their FAQ here.
How do I use Polygon/Matic on OpenSea?
In order to use the Polygon/Matic on OpenSea, you will need to "bridge" or transfer your Ethereum (ETH) onto the MATIC network.
You can do this by heading to the wallet icon, located on the top-right of the OpenSea website. You should already have some ETH in your account. Click here to learn about how you can purchase ETH.
Once you have ETH in your wallet, click on the three circles on the right. You should see a button, "Bridge to Matic".
After clicking it, a pop-up window will appear and you can enter how much ETH you would like to bridge onto Matic.
You'll be asked to sign a transaction on MetaMask.
Once you've signed the transaction and it's completed, you should see a window like below.
The bridging process from Ethereum to Matic takes approximately 7 minutes. Once it's successful, you'll see a purple ETH icon representing your bridged ETH on Matic.
Now that you've transferred ETH onto Matic, click here to learn how to buy your first NFT on Matic.