Every template carries a category. It determines what the message may contain and what Meta charges for it, and picking the wrong one is a common cause of rejection.
Marketing
Promotions, offers, product announcements, abandoned-cart nudges, anything intended to sell. The most expensive category, and the one requiring the clearest opt-in.
Utility
Messages about a transaction that already exists: order confirmations, delivery updates, appointment reminders, receipts. Cheaper than marketing, because the customer is expecting them.
Authentication
One-time passcodes and verification codes only. Nothing else may travel in this category.