thank you all guys, so if i am buying the erc20 from binance i am not paying the gas fees?
i pay it only if i move it within a dex?
You don't pay the gas fee if you just keep your erc20 within binance exchange platform or wallet but if you want to withdraw it to your own personal address then you need to pay the gas fee and usually platform like binance charges gas fee higher than average. the way it works is that using cex you dont interact with the blockchain but exchange system but with dex you interact with the blockchain.