The ‘back-end’ is referred to as the part of a website or web service that the user cannot see in the browser such as web servers, applications and databases. ‘Back-end’ in the web industry is also commonly called ‘server-side’. Typically the back-end code is comprised of one or more programming languages.
A back-end developer builds and maintains the technology that powers the servers, applications and databases, which together, enable to user-facing side of the website to exist. A back-end developer or programmer work on items such as security, structure and content management. They develop and use many different languages and technologies such as Javascript, Ruby, Java, PHP, .NET, and Python, as well as SQL, Oracle and more. Although most back-end programmers understand HTML and CSS it’s not their focus.