Definition
A WhatsApp Business Account (WABA) is the Meta asset that represents a business on the WhatsApp Business Platform. It holds the business phone numbers and message templates, and every API message is sent through a WABA.
Meta's documentation states that you must have a WABA to send and receive messages and to create and manage templates. A WABA belongs to exactly one Meta business portfolio, and it cannot be moved from one business portfolio to another.
Meta's documentation currently lists these limits: a Messaging account (which now holds a WABA's templates) can have up to 250 message templates while the business portfolio is unverified, or up to 6,000 once the portfolio is verified and has a number with an approved display name; a business starts with 2 registered business phone numbers per WhatsApp account hierarchy, which can be raised to 20; and it is initially limited to 20 WhatsApp account hierarchies. Meta is splitting the WABA into a WhatsApp account and a Messaging account, so check the current figures in Meta's documentation, because they change.
Most businesses create a WABA through a partner's Embedded Signup flow, which also creates or selects the business portfolio and registers the phone number. A WABA can be shared with up to two partners, and the business keeps ownership of the assets.
Practical tips: set the WABA's time zone and currency carefully, because they cannot be edited once a line of credit is attached. Also keep separate WABAs for clearly separate brands rather than mixing them, since templates and quality signals are managed per WABA.