@vue/cli-service is the official development server and build tool for Vue.js applications bootstrapped with Vue CLI. It handles the essential tasks of compiling, bundling, and optimizing your code, providing a seamless development experience. Features include hot module replacement for instant updates, built-in support for popular libraries like Babel and PostCSS, and optimized production builds with code splitting and asset optimization. It simplifies the complex configuration process, letting developers focus on writing Vue code.