Next.js Subscription Starter is a subscription starter template provided by Vercel, Stripe, and Supabase. It provides the basic structure and functionality for building web applications with subscription features. This template uses Next.js as the front-end framework, Stripe as the payment processing platform, and Supabase as the back-end database and authentication solution. You can use this template to quickly build an application with subscription features and easily manage your users' subscription plans.