Nexmo is a cPaaS (Communications Platform as a Service) that offers SMS/Voice/Authentication communications to its customers. You can use Nexmo's Communications APIs too.
Read the official documentation of Nexmo which is now Vonage here.
Nexmo on Connect iPaaS¶
Connect iPaaS enables you to integrate Nexmo with other SaaS and enterprise applications. You can build a workflow to call or send SMS through Nexmo based on certain events in other applications. Conversely, you can perform actions on other applications based on SMS received in your Nexmo system.