Hey Dave! Here, window.ethereum is actually the MetaMask provider. From there, once you've connected the provider you can use web3.js to interact with contracts and your wallet. For example, once you've initialized web3.js with window.ethereum using the steps in the article, you can do things like "await web3.eth.getAccounts()" to get your wallet addresses.

Hopefully that clears things up! Happy to chat in our discord as well, would love to have you there! https://valist.io/discord