The Zoko WhatsApp Business API makes 3 types of communication possible.
Incoming Session Messages — Any message received from the customer is an Incoming Session Message. Any incoming message from the customer opens up a 24-hour customer service session.
Outgoing Session Messages — Any message sent by the business to customers, within 24 hours of an Incoming Session Message becomes an Outgoing Session Message.
Outgoing Template Messages — If it has been 24 hours since the last Incoming Session Message from the customer, OR if the customer has never messaged the business, then the business can send only an pre-approved Outgoing Template Message.
Outgoing Template Messages have to be submitted to WhatsApp for approval. The review process can take up to 48 hours. Once approved by WhatsApp, the business can technically send Outgoing Template Messages to any customer at any time, regardless of whether there has been an incoming message from the customer or not.