Thymeleaf is a modern server-side Java template engine used for web and standalone applications. It allows developers to create dynamic web pages by integrating HTML with Java code, making it easier to generate content based on user input or database information. Thymeleaf supports natural templating, meaning that the templates can be rendered as static files, which is useful for design and development. One of the key features of Thymeleaf is its ability to work seamlessly with the Spring Framework, enhancing the development of web applications. It provides a rich set of attributes for processing data, enabling developers to create interactive and responsive user interfaces without extensive JavaScript.