Gwei pertains to an Ethereum denomination used within the Ethereum blockchain.
Also called nanoether, or nano, the Gwei refers to the power of the fractional ETH. Thinking of a Gwei visually is impossible as its actual size is imperceptible. This is the case as the cryptocurrency is only used for writing codes and other technical cases.
Gwei is actually the most used Ether unit as “gas” prices are easily quoted through Gwei. For instance, it is easier to say that one’s gas costs 1 Gwei rather than saying your gas costs 0.000000001 Ether.
The term Gwei is actually shorthand for Gigawei or 1,000,000,000 Wei.