“Web development is a broad term for the work involved in developing a web site for the Internet (World Wide Web) or an intranet (a private network) . This can include web design, web content development, client liaison, client-side/server-side scripting, web server and network security configuration, and e-commerce development. However, among web professionals, “web development” usually refers to the main non-design aspects of building web sites: writing markup and coding. Web development can range from developing the simplest static single page of plain text to the most complex web-based internet applications, electronic businesses, or social network services.” (Wikipedia)

and

“Web design is the skill of creating presentations of content (usually hypertext or hypermedia) that is delivered to an end-user through the World Wide Web, by way of a Web browser or other Web-enabled software like Internet television clients, microblogging clients and RSS readers.” (Wikipedia)

Basically, in layman’s terms: web design is based on the FRONT end layout people see when they visit a website, and web development focuses on design and function of the front AND BACK end, languages, server scripting, databases, etc.