PHP is an open-source server-side scripting language used for web development. It allows programmers to embed PHP code into HTML pages which is executed on the server to generate dynamic web pages. PHP scripts are interpreted at runtime rather than compiled, making it compatible with many databases and operating systems. PHP works with web servers to deliver dynamic HTML content to users. It is a cost-effective option for developing websites, web applications, and integrating with content management systems and payment gateways. Training in PHP covers topics like syntax, variables, data types, operators, loops and frameworks over 6-12 month programs.