ASP is a server-side scripting language developed by Microsoft. Designed to run on Windows hosting, ASP produces dynamically created webpages, allowing developers to create complex and interactive websites and web-based applications.
Most ASP is written in VBScript and can only be run on Windows server platforms, with many web pages ending in .asp. ASP is separate from ASP.NET, as ASP is interpreted and run when the users interact with the page, whereas ASP.NET is compiled for faster and more robust running.
You can find out more about ASP on the Microsoft Developer Network: http://msdn.microsoft.com/en-us/library/aa286483.aspx.