OTP (One-Time Password) SMS is a security mechanism that provides an additional layer of authentication for online transactions, such as logging into a website or making a payment. When you initiate a transaction, the website or service sends an OTP code to your registered mobile number via SMS. You then enter the OTP code into the website or app to confirm your identity and complete the transaction.

The OTP code is typically a randomly generated numeric code that is valid for a short period of time, usually only a few minutes. This ensures that the code cannot be reused or intercepted by an attacker.

OTP SMS is a widely used method of two-factor authentication, which is considered more secure than traditional username and password authentication. By requiring users to provide a unique code in addition to their login credentials, OTP SMS helps to prevent unauthorized access to online accounts and transactions.