Typically, users need to pay a fee for $ETH or ERC20 tokens withdrawal from CEX to Ethereum, since the gas is expensive.
But in FTX, if you stake $FTT, the native token of FTX, you will get free $ETH and ERC20 withdrawals, 3~1000 times a day depending on the staked amounts.
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In EVM, a special function -- the fallback function -- is executed whenever contracts receive $ETH. And the user who sends $ETH to the contract pays the gas fee for the execution.