A programming language is a set of functions and syntax that allow you to write programs.
Compiled vs Scripted
A compiled language, such as C or Java, compiles application code into a binary, which is then executed.
A scripted language is compiled at runtime. What this means for web languages is that we can update the code and refresh the page, whereas compiled languages require an extra build step.
Markup
HTML is a text markup language, meaning a syntax for defining attributes for text and data so that it can be interpreted.
XML is also a markup language, which is what HTML is derived from.
PHP
PHP Hypertext Processor - a recursive acronym, referring to an HTML processor.
Early on the web, PHP was commonly used as a templating and scripting language. Developers could get started by changing their HTML files into .php and replacing static content with variables and logic.
Over time, PHP has become a modern object oriented language. The available libraries and frameworks are mature and extensive, and keep up with programming best practices.
Javascript
Originally created for interactive features in the browser. Javascript is quickly taking on a bigger role in the front and back end.
Node is Javascript running on the server side, which allows developers to code in one language.