Promotional SMS :
These smses are those which is used to promote Sales and Marketing business,Product Offers and Promotions to any random users with some restriction. You can send sms between 9:00 am to 9:00 pm. These messages are only delivered to Non DND users.
Transactional SMS :
These kind of messages are used to send necessary information to the customers or users. for example a school send sms to their students, similarly a bank send alert messages to their users , in the same way a company send messages to their client regarding invoice amount of using their product and services.