An SMSC receives, stores, forwards, and delivers text messages. It helps mobile devices speak to each other over wireless networks. Here’s a quick example: 

David sends a text message to Patrick. The SMSC receives the message. Patrick’s phone is turned off so, the message is stored in the SMSC. When Patrick turns his phone on, the SMSC delivers the message. If Patrick’s phone had been turned on when David sent the message, the SMSC would have forwarded the text straight to him. 

The importance of Short Message Service Center - SMSC 

An SMSC’s job is to route and regulate message sending, but they can also tailor service delivery to improve efficiency.  

Banking notifications, for example, can be time-sensitive and need an aggressive retry scheme in place to deliver critical messages ASAP. But less urgent messages don’t need this kind of backup. Retry rates can be configured to suit individual business needs in an SMSC.