Google Calendar is an get a button on its browser toolbar that they can easily click to see upcoming events from google calendar, without ever leaving their page. And if they are on sites that have special events encoded, it can click the button to instantly add events to they calendar.
PHP: Hypertext Preprocessor is a server-side scripting language designed for Web development, but also used as a general-purpose programming language. PHP code may be embedded into HTML code, or it can be used in combination with various web template systems, web content management systems, and web frameworks.
The Prototype JavaScript Framework is a JavaScript framework as part of the foundation for Ajax support in Ruby on Rails. It is implemented as a single file of JavaScript code, usually named prototype.js.
script.aculo.us is a JavaScript library built on the Prototype JavaScript Framework, providing dynamic visual effects and user interface elements via the Document Object Model (DOM). It is most notably included with Ruby on Rails and Seaside, but also provided separately to work with other web frameworks and scripting languages.