PHP stands for Hypertext Preprocessor. It is a widely used open-source server-side scripting language designed especially for web development. PHP is used to create dynamic and interactive websites.

Unlike HTML, which only structures content, PHP runs on the server and can process data, interact with databases, manage sessions, and generate dynamic page content before sending it to the browser.

PHP is commonly used for:

• Creating login and registration systems
• Handling form data
• Connecting to databases like MySQL
• Building dynamic web applications
• Managing sessions and cookies

PHP code is embedded inside HTML and executed on the server. The server processes the PHP code and sends the final output (usually HTML) to the user's browser.

Because of its simplicity, flexibility, and strong community support, PHP is one of the most popular languages for backend web development. Many well-known websites and applications are built using PHP.