Front-end Development
Producing the user-facing code of a website that instructs the rendering engine what to draw on screen. I started out using HTML 3.2 in 1997 (when we used to use tables for everything), and can now make advanced layouts that adapt to any screen size.
Using HTML, CSS, and JavaScript anything is possible. The key to making a usable, functional and responsive layout is to optimise the HTML elements used, produce modular CSS using the BEM naming convention, and understand how an JavaScript will interact with the page to optimise selector usage, and lean on CSS to transform elements on the page.