When a user wants to send ETH or tokens, they must include a gas fee to cover the cost of the transaction. The gas fee is calculated based on the amount of data included in the transaction, and the gas price, which is set by the user.
The gas price is usually denominated in Gwei, which is worth 0.000000001 ETH.
So, if the gas price is 20 Gwei, then the total gas fee would be 0.000002 ETH. .
The actual amount of ETH that is sent can be more or less than the amount of ETH specified in the transaction, depending on the gas price. If the transaction fails, then all of the ETH in the gas fee is still sent to the recipient.