Stencil is a toolchain for building reusable, scalable web components. Developed by the Ionic team, Stencil allows developers to create custom web components using modern web standards like TypeScript, JSX, and Web Components APIs. These components can then be used in any JavaScript framework or library, such as Angular, React, or Vue.js, or integrated directly into traditional web applications. Stencil emphasizes performance, simplicity, and compatibility, enabling developers to build high-quality, interoperable components for their web projects.