Web design is the process of creating a visual representation of a website using tools such as graphic design, HTML and CSS. It is focused primarily on the aesthetics of a website and how it will look and feel to the user.
Web development, on the other hand, takes the design and turns it into a working website. It involves coding, using a range of programming languages such as HTML, JavaScript, PHP and more. Web development also includes setting up databases and creating content management systems so that users can update their websites without having to write code.