Making sense of "bitcoin wallet app" starts with what a wallet actually holds. A bitcoin wallet is an app or a small device that keeps the private keys for coins recorded on the bitcoin network; the coins never sit in the wallet itself. For someone about to pay a casino in crypto, the wallet is the first tool to set up. A few decisions taken in its first ten minutes shape everything after: who keeps the keys, which networks it handles, and which device carries it.
A bitcoin wallet on a phone suits small, frequent transfers, since the camera can scan the address code a casino cashier shows. The phone is also the weak point: it can be lost, stolen or infected, so a screen lock, current updates and a modest balance keep the risk within reason. A bitcoin wallet app belongs on the device only from the official app store or the developer's own site, checked by the developer's name. Fake copies borrow known names and icons, and no app stays safe once its backup words have been typed somewhere else.
A USDT wallet is any wallet that supports USDT on the network being used, because USDT runs on several networks, among them TRC20 on TRON, ERC20 on Ethereum and BEP20 on BNB Smart Chain. A balance on one network does not move to another by itself. To create a USDT wallet, set up the app as usual, back up the words, then add USDT and choose the network before copying the address. Fees are paid in that network's coin: TRX on TRON, through energy and bandwidth or TRX burnt for them, ETH gas on Ethereum, BNB on BNB Smart Chain.
Other questions
Is a bitcoin wallet on a phone a good idea?
For small, frequent transfers it is practical, as long as the phone has a screen lock, current updates and only a modest balance on it.
Where should a bitcoin wallet app be downloaded?
Only from its listing in an app store or the developer's own site, checked by developer name, since fake copies imitate known names and icons.
How do I create a bitcoin wallet?
Install a wallet app from its official source, let it generate keys, copy the backup words onto paper, and only then use the receiving address it shows.
Is Trust Wallet safe to use?
It is a self custody app, so its safety rests mostly on the owner: an official download, a locked phone and a recovery phrase nobody else sees.
What is needed to send USDT from a new wallet?
The right network chosen before copying the address, plus some of that network's coin for fees: TRX on TRON, ETH on Ethereum, BNB on BNB Smart Chain.