Ether (ETH) is the cryptocurrency used on the Ethereum network. When you use Ethereum to send money or run programs on the network, you need to pay a small fee. Gwei is like a tiny denomination of Ether, kind of like cents to a dollar. It's used to specify how much you're willing to pay for your transaction to be processed on the Ethereum network. The lower the gwei price you set, the longer it might take for your transaction to be completed.
