PHP is a scripting language used for web development that allows developers to write dynamically generated web pages quickly. It reduces the time to create large websites and allows users to have customized experiences based on gathered information. Basic knowledge of HTML and programming concepts helps in learning PHP. PHP code is written within HTML using <?php ?> tags and variables are defined with a $ and used to store and reuse values throughout code. Comments are added with // for single lines and /* */ for multiple lines. HTML forms can be created to gather user input which is processed using the $_POST superglobal variable in PHP.