They are so many types of messages will be sent to users, here are few
• Promotional Messages
• Business Messages
• Transactional Messages
• Informational Messages
• Service Messages

To Avail Bulk SMS Services DLT registration is Mandatory as of TRAI Rules
DLT registration refers to the process of registering on a Distributed Ledger Technology (DLT) platform as mandated by the Telecom Regulatory Authority of India (TRAI). In India, TRAI has implemented regulations to curb unsolicited commercial communications, such as promotional SMS and calls, and to protect the privacy and preferences of consumers. You will have to pay Rs. 5,900 as a one-time DLT registration fee on the first platform where you register. After that, additional registrations on any other platform mentioned above are free of cost.

Instant and Direct Communication: Bulk SMS enables you to reach your audience instantly and directly. Text messages are usually read within minutes of being received, making it an effective way to deliver time-sensitive information, promotions, or important updates.

High Open and Response Rates: SMS messages typically have high open rates, with studies indicating that the open rate for text messages is around 98% compared to email's average open rate of around 20%. Additionally, SMS messages tend to have higher response rates, making it an effective channel for engagement and interaction.

Wide Reach: SMS messages can reach a broad audience as almost everyone owns a mobile phone, and text messaging is a widely used communication method. It allows you to communicate with individuals who may not have access to email or other forms of digital communication.

Cost-Effective: Bulk SMS is generally more cost-effective compared to other marketing channels, such as print advertising or direct mail campaigns. The costs associated with sending text messages are typically lower, making it a budget-friendly option, especially for small businesses.

Personalized and Targeted Communication: With bulk SMS, you can personalize messages by addressing recipients by their names and customize content based on their preferences or past interactions. Moreover, you can segment your audience and send targeted messages to specific groups, enhancing the relevance and effectiveness of your communications.

Automation and Integration: Bulk SMS services often provide automation features, allowing you to schedule messages in advance or trigger messages based on specific events or actions. Furthermore, many SMS service providers offer integrations with other systems, such as customer relationship management (CRM) tools or e-commerce platforms, enabling seamless data syncing and campaign management.

For more details please check this article to get more information about Bulk SMS Services and TRAI Rules SMS Services and Its Requirements