How these temporary numbers work
Each number is a virtual line: an incoming SMS is routed over the internet to the number's page rather than to a physical SIM. Open a number, refresh, and the verification code appears in the message list within about a minute.
What you can (and can't) use them for
They are ideal for one-time verifications, sign-ups and free trials where you would rather not give out your real number. Because they are shared and public, never use them for banking, password resets or anything sensitive.