What is the difference between web design and web development?
According to my keyword research (SEO stuff!), the broad terms web design and web development are nearly interchangeable. Both boast near equal amounts of monthly traffic and both branch out into similar long-tail keywords. This hints that the general public might not see a difference between web designers and web developers. But if we were to get picky with definitions, there is a traditional difference that matters, well, it would at least matter if you were applying for a formal job.
Web development vs Web Design, the short version.
Web designers typically deal with the content of a website. For example, they play around with different potential layouts for your website based on your current content / future content and decide what works best. During the design stage, they need to consider various important things, such as your your brand identity; they need to make sure that the colour pallet and any other particular styles your brand maintains is found throughout your website. In short, the emphasis here is the design part.
Their work is mocked-up in a program like Adobe Photoshop or Adobe Illustrator and later given to the web developer.
If you're interested in learning a bit more about the design principles web designers use, check out our short 5 part series: intro to graphic design.