EJS (Embedded JavaScript) is a simple templating language that lets you generate HTML markup with plain JavaScript. It's commonly used in Node.js environments for creating dynamic web pages on the server-side. EJS files contain a mix of HTML and JavaScript code, where the JavaScript code is embedded within special tags. These tags allow you to insert data, perform calculations, and control the flow of the template rendering process. When an EJS file is processed by an EJS engine, the JavaScript code is executed, and the results are inserted into the HTML, producing the final HTML output. EJS is known for its simplicity and flexibility, making it a popular choice for developers who want a straightforward way to generate dynamic content. It supports various features like including partial templates, defining custom delimiters, and caching compiled templates for improved performance. EJS is often used with frameworks like Express.js to build web applications.