Can we say that
gas is the unit of transaction fee ?
gas price is the same transaction fee ?
If so, why we do not use
wei instead of
in a nutshell :
gas is the cost unit
gas price is a single gas unit's price
Fee= gas*gas price
why using gas instead wei?
because we need a fixed value (unit) for expressing the operations cost. then this initial cost is "translated" in wei/ether which may vary according to the market.
"y operation"= x gas => x gas * market gas price= your fee (Z).
so "y operation" cost will be always x gas, today as in next year, but z will change as the gas price will change.