Behind "What is an ethereum wallet?" sits one idea: the coin is the same, the road it takes is not. USDT TRC20 is the version of USDT issued as a TRC20 token on the TRON blockchain, and it is one of the most common ways to send USDT because fees there are usually low. The same coin also exists as BEP20 on BSC and as ERC20 on Ethereum. Each version has its own fees and rules, and a balance on one network never moves to another on its own.
What is the ERC20 network? ERC20 is the token standard on Ethereum, and the ERC20 network is the everyday shorthand for sending such tokens on Ethereum. USDT ERC20 is the version of the coin issued under it, and many exchanges support it. Its fees are paid in ETH as gas: the gas a transfer uses multiplied by the gas price at that moment, which can climb sharply when Ethereum is busy. A wallet the owner controls usually needs some ETH to send ERC20 tokens at all, unless a service sponsors the fee or another party pays it.
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.
BNB, the native coin of the chain, so a wallet sending BEP20 tokens needs a little BNB.
Not reliably. Addresses on BEP20 and ERC20 share the 0x format and may match exactly, so the network is picked from the list and matched on the receiving side.
Its network list for sending and receiving should name TRC20 or TRON explicitly; supporting USDT alone says nothing about the network.
A TRON address usually starts with the capital letter T, unlike the 0x addresses of Ethereum and compatible chains.
ETH, as gas: the gas the transfer uses times the gas price at that moment, which rises when Ethereum is busy.