Front-End Development refers to a person who specializes in certain web technologies, that pertain to the interaction between the user and a website or web application. These technologies include HTML (HyperText Markup Language), CSS (Cascading Style Sheets), and JavaScript. These technologies are responsible for the structure, styling, and behavior of a website.

To help complement this question, I would like to quote Ivan Codesido’s article What is front-end development? on guardian.co.uk (see original article here.)

In our visually and tecnhologically sophisticated society, access to information and knowledge seems easier than making sense of it or decide its veracity - on the web, pages and appplications are built by front-end developers to present and put data or relationships in context.

Front-end or client-side development is a relatively obscure Internet discipline. Historically, this role has been known under several aliases, htmler, web designer, coder, frontender and so on, but its core functions remain the same while expanding with the progress of the Internet. It is a hinge role that requires both aesthetic sensitivity and programmatic rigor.

To many people, client-side development might be perceived as ‘making things pretty’ and, while it is a valid comment since we do make things look good, as good-looking things sell better, there are many other technologies that fall within this field that might be usually overlooked.

Front-End Developers are in charge of creating the face of a website, and the way that face speaks to its audience. Take Steve Jobs’ words for it.

Design is not just what it looks like and feels like. Design is how it works.