Prototype is a JavaScript framework that aims to ease development of dynamic web applications.
It defines both generally useful functions for Javascript development, as well as some pieces for doing actual AJAX interactions.
See http://www.sergiopereira.com/articles/prototype.js.html for some good documentation.
This monkey patch by kangax allows you to get sense from inspecting a constructor setup via Prototype.
His code changes a simple person class from:
too:
If you want more help with Prototype and Script.aculo.us you can check out their newly changed support list.