There are two components which deliver a website.
- The web server which holds the site information
- The browser program used to view the site (Internet Explorer, Firefox, Chrome, etc.).
Every web developer has an understanding about both components, but many developers choose to focus on one of those components for their career. Since you are just starting as a web developer it would be good for you to learn a bit about both, then choose your area to focus on.
Web Development on the Server
Web developers who work on code on servers write the code which constructs the website. Their code pulls data and files from the server and combines them to produce the website.
Their code tells the server what to do when you send data to the server. Such as when you submit a form or send an email.
Web developers who work on server based code are often referred to as Back-end Developers.
Web Development for the Browser
Web developers who work on code on for the web browser write code which tells the browser where to lay out the pieces of a webpage. Their code tells the browser where to put text, images, and media (video, slideshows, etc.) on a given webpage.
Web developers who work on browser based code are often refereed to as Front-end Developers.