What is the BEP20 network? Strictly, BEP20 is a token standard on BSC rather than a network of its own, though wallets and cashiers list it as one. USDT BEP20 is the version of USDT issued under that standard, and its fees are paid in BNB, the native coin of the chain, usually at low cost. Addresses on BSC start with 0x exactly as Ethereum addresses do, and one address can exist on both chains. The look of an address therefore never shows which network a payment will travel on.
What is the TRON TRC20 network? TRON is a blockchain with its own coin, TRX, and TRC20 is the token standard under which other coins, USDT included, are issued on it. TRX and TRC20 are different things: one is the native coin, the other is a format. TRON counts fees in resources called energy and bandwidth. An account uses the resources it holds or has been delegated, and when they run short the network burns TRX to cover the gap, so one transfer can cost different amounts from one account to the next. TRON addresses usually start with the letter T.