Web design is the customer-facing part of the website. A web designer is concerned with how a site looks and how the customers interact with it. Good web designers know how to put together the principles of design to create a site that looks great. They also understand about usability and how to create a site that customers want to navigate around in because it’s so easy to do. This should be seen as auto body work. You are working on the exterior (front end) features of your Website.
Web development is the back-end of the website, the programming and interactions on the pages. A web developer focuses on how a site works and how the customers get things done on it. Good web developers know how to program CGI and scripts like PHP. They understand about how web forms work and can keep a site running effectively. Web development often refers to data driven Websites but also refers to other automated features such as mail scripts.