A short-lived number for one verification code, so your personal number stays out of databases and marketing lists.
A temporary number is assigned to you for one order. It exists long enough to receive the verification SMS, then it goes back to the pool. Treat it as borrowed, never as an identity. Do not attach it to an account you cannot afford to lose.
Avoid temporary numbers for banking, payments, government services and any account that matters long term. Those need a stable number registered to you. If you expect to receive more codes later, use a rental number instead.
For the order window. Once you receive the code or cancel, the number is released.
Not a one-time number. Choose a rental if you may need more codes.
Using a virtual number for privacy and testing is lawful in most places, but you must follow the terms of each service and local rules. Never use it for fraud or abuse.
Registration is free. Test one order, check that your app accepts the number, then top up only what you need.