ASP stands for Active Server Pages and is a Microsoft technology that allows for server-side scripting. ASP files contain HTML, text, scripts and other markup. When a browser requests an ASP file, the ASP engine in IIS or PWS executes the scripts and returns an HTML page to the browser. ASP allows for dynamic web pages, accessing databases, customizing content for users, and providing security since scripts are not visible to browsers. IIS is required to run ASP and can be installed on Windows Vista by turning on the Internet Information Services feature in Programs and Features.