Types of Messages on WhatsApp API
This page provides an overview of how messages work on the WhatsApp Business API.
Currently, we support sending two types of messages:
User-Initiated Messages
You can send responses to user-initiated messages. You may respond to user messages with any type of message within 24 hours from the time last customer message is received. This 24-hour period is known as the response window
Business-Initiated Messages
At any time, you can send business-initiated messages to customers who have opted-in. Throughout the documentation, these messages are also called notifications, message templates, or templated messages.
When sending business-initiated messages, you are required to use a pre-approved message template, which can be text-based, media-based, or interactive. Your template must fall under one of the following categories:

Business-initiated messages must be transactional and promotional messages are not permitted.