A templating engine is a tool used in web development to generate dynamic HTML pages by combining templates with data. It allows developers to create reusable templates that can be filled with specific content, making it easier to manage and update web applications. Popular templating engines include Mustache, Handlebars, and EJS. These engines work by using placeholders, often enclosed in curly braces, to represent dynamic content. When a template is processed, the templating engine replaces these placeholders with actual data, producing a final HTML output. This approach helps separate the presentation layer from the business logic, improving code organization and maintainability.