tRPC is a powerful TypeScript library that allows you to build type-safe end-to-end APIs without schemas like REST or GraphQL.The project stack for building full-stack apps includes Next.js 15, TypeScript, TailwindCSS, Zod for validation, and React Query for data fetching.The tRPC backend setup involves creating a tRPC server and defining routers and procedures for handling API requests.By using tRPC with Next.js, developers can benefit from full type safety, faster development workflow, and no need for API schemas.