Polkadot is a pretty interesting cryptocurrency. Like Ethereum smart chain, Binance smart chain, and Kucoin Smart chain, other cryptocurrencies can be built upon it’s network. A list of existing coins can be reviewed here although many of these cryptocurrencies/tokens are on multiple networks: https://coinmarketcap.com/view/polkadot-ecosystem/ I think Reef started out as Polkadot only, IIRC.

When auditing smartchain coins, I find it best to answer the following two questions: 1) are the applications or coins people are developing on it good? And 2) Is my own smart contract development on it likely to be a good experience?

If you own Polkadot, you can and should be staking it somewhere for 12-16% annual interest.