Gwei

Gwei is a small denomination of ether (ETH) used mainly to quote gas prices on Ethereum. One gwei equals one billionth of an ETH (0.000000001 ETH), or 1,000,000,000 wei, wei being the smallest unit of ether. The name comes from "giga-wei".

When your wallet shows a gas price of, say, 2 gwei, it means you will pay 2 gwei for every unit of gas your transaction uses. A simple ETH transfer uses 21,000 gas, so at 2 gwei it would cost 42,000 gwei, or 0.000042 ETH. A complex DeFi swap might use ten times as much gas.

Quoting prices in gwei makes small numbers easier to read, in the same way that bitcoin fees are quoted in satoshis per byte. Gas prices on Ethereum's main network vary with demand; on layer-2 networks they are usually a tiny fraction of a gwei. Other EVM chains such as BNB Chain and Polygon also use gwei for their native coins.