Etherscan is a tool to help you view data regarding any pending or confirmed Ethereum blockchain transactions. Since Ethereum is a public, open blockchain, whenever anyone interacts with it the action is recorded into the transaction history and it is open for anyone to see. Etherscan is a very useful resource because it helps you navigate through this data to make better sense of where your ETH is going.
In order to look up your wallet, copy and paste your public wallet address into the search bar at the top of their home page. Once you submit this, you will be taken to a page that shows key metrics for your wallet, such as ETH balance and corresponding USD value, and your full history of transactions.
Etherscan can also be used to monitor the status of a pending transaction. When you initiate a transaction in MetaMask and go into the “Details” section for the particular transaction, MetaMask links to the transaction hash’s Etherscan page, which gives you an estimate of how long the transaction will take to confirm and also updates when the transaction does get finalized.
Keep in mind that, while all of the information on the Ethereum blockchain (and therefore Etherscan) is public, only your public wallet address is displayed.