Gas fees explained without the jargon
Gas, gwei, limits and priority fees, in plain terms. What you actually control, and why the same transfer costs different amounts.
Gas is Ethereum's way of charging for computation. Every operation costs a set amount of gas, and you pay for the gas your transaction uses at whatever price the market is asking.
Two numbers, multiplied. That is the whole idea, and the confusion comes entirely from the vocabulary around it.
The two numbers
Gas used is fixed by what you are doing, not by you. A simple ETH transfer costs 21,000 gas. Moving an ERC20 token costs more because a contract has to run. Complex contract interactions cost more again.
Gas price is what you bid per unit, quoted in gwei — a billionth of an ETH. This is the part that moves with demand, and the part you can influence.
Fee = gas used × gas price. A busy network does not change how much gas your transfer needs; it changes what each unit costs.
Limit, base fee, priority fee
The gas limit is a ceiling you set so a runaway contract cannot drain your wallet. For a plain transfer the wallet fills it in correctly and you should leave it alone.
The base fee is set by the protocol from recent demand and is burned. The priority fee is a tip to validators, and raising it is how you jump the queue when you are in a hurry.
If a transaction runs out of gas it fails, and you still pay for the gas consumed before it stopped. That is the one case where you pay for nothing, and it is why leaving the limit alone matters.
What this means for you
If you are moving stablecoins and have a choice of network, that choice dwarfs every gas optimisation available. TRC20 does not have gas in this sense at all.
If you are on Ethereum by necessity, send when the network is quieter and leave the limit at the default. Those two habits cover almost all of the realistic saving.