Answer
Authentication is the process of verifying identity (or control of an account) before granting access to an action.
Common factors:
- password (something you know);
- phone OTP (something you have — SIM/messenger);
- device / biometrics (something you are / have).
In SaaS and fintech, OTP often sits on registration, login, password reset, and payment confirmation. It is not a substitute for antifraud and KYC, but a phone-confirmation layer.
Cascade covers delivery of the OTP factor: you call the API, the user gets a code on their number. More about the code itself: “What is OTP?”. About the API token: Bearer, key security. Product scenario: /use-cases/saas.