Welcome to RCX4! On this website you will find both desktop and web applications.
Desktop applications are mostly written in C# and/or C++, whilst the web apps are built using PHP, Javascript and/or Ajax.
Here are some quick details about these programming languages:

PHP: Hypertext Preprocessor (a recursive acronym, originally personal home page) is a general-purpose scripting language that was originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document. As a general-purpose programming language, PHP code is processed by an interpreter application in command-line mode performing desired operating system operations and producing program output on its standard output channel. It may also function as a graphical application. PHP is available as a processor for most modern web servers and as a standalone interpreter on most operating systems and computing platforms.
PHP was originally created by Rasmus Lerdorf in 1995 and has been in continuous development ever...