Many people use the two terms “web design” and “web development” interchangeably, but they really do have two very different tasks.
A web designer is responsible for the aesthetic design of the website (they radiates creativity, and have no problems in dealing with typography, user interface design and usability, etc.) as well as convert the client’s vision to artistic design.
A web developer is more of a technical expert with programming skills. They speak a different language (or more than one, programming language that is) than front-end designers.
Designers and developers each have their own unique skill sets. This post explains more on who fits your need on your next project.