Header is a combination of six characters representing your brand or company. Depending on the purpose of the SMS, the header can be classified as Promotional, Transactional, Service Implicit and Service Explicit.
For sending marketing or promotional SMS, such as offers, discounts, or promotions, you need to choose the "Promotional" category and choose a six-digit numeric sender ID, which will be prefixed with your business. Along with that, you need to attach proof of your business for verification.