Courier, Segment, and Twilio form a powerful combination that enables developers and companies to deliver personalized notifications to users across multiple channels without building their own infrastructure. Segment provides a unified view of customer data, while Twilio offers communication APIs for voice, SMS, video, WhatsApp, and email. Courier sits between these two platforms, providing an orchestration layer that enables the connection of customer data to communication channels through a no-code interface, abstracting away channel integrations, template management, workflow orchestration, user preferences management, and logs and analytics capabilities.