Segment is a customer data platform that helps businesses collect, clean, and control their customer data. By providing a single API, Segment allows companies to send their data to hundreds of tools and systems, enabling them to create a cohesive and comprehensive view of their customers' interactions across different platforms. A subscription to Segment typically includes features such as data collection and integration, identity resolution, audience building, and analytics, which help in creating personalized customer experiences and gaining actionable insights.