A Message Template is what you need to send a Template Message!
A Message Template is the pre-approved templates submitted in your WhatsApp template manager.
Depending on your subscription, a certain amount of templates can be registered in your template manager.
For more details, please check the article Message Templates
Once your Message Template is approved, you can send a Template Message to your customer to initiate the conversation.
For these messages, a transactional fee will be applied. You can find a further explanation on pricing in How do we calculate WhatsApp pricing.