Mobile SMSes in the current world are still predominantly used by marketers for they have a good open rate vis-a-vis other modes of communication channels.
SMS (Short Message Service), commonly referred to as "text messaging," is a service for sending short messages of up to 160 characters (224 characters if using a 5-bit mode) to mobile devices, including cellular phones, smartphones and PDAs.
Users can send messages from a computer via an SMS gateway. SMS gateways are Web sites that allow users to send messages to people within the cell served by that gateway. They also serve as international gateways for users with roaming capability.
Transactional SMS are messages which are sent to your customer to pass on information necessary for using your product or service.
Promotional SMS are SMSes which are sent with the objective of promoting your product or service. This category includes any sales & marketing messages which may or may not be solicited by the recipient.