A web developer is a professional who specializes in the development of web applications and websites. They are responsible for creating and implementing the technical aspects of a website, including the design, layout, and functionality. Web developers typically use languages such as HTML, CSS, JavaScript, and PHP to create and maintain websites, as well as frameworks and content management systems to make development faster and more efficient. They also test and debug code to ensure that the website or web application is functioning correctly and is compatible with different web browsers and devices. They may also be involved in the maintenance and updates of the website as well as the optimization of the website for better performance and user experience.