Staking your coins is one of the foundations of Hex. When you stake your coins, you are locking them up by burning them. The coins you stake are no longer a part of the circulating supply, so they cannot be bought or sold. When you stake, you earn a portion of the share pool. It is through these shares that you earn interest.
Please reference the Staking guide.
You can see all your active stakes on go.hex.win, or hex.live. To see them, you must connect your metamask wallet to either site.
You can switch between different MetaMask wallets and you should see your active stakes update to the ones on the currently selected wallet.
Here you can also see your accumulated interest, total shares, estimated Big Pay Day bonus based on current day data, and maturity of your stake.