Prototype.js is a JavaScript framework created in 2005 by Sam Stephenson and the Prototype Core Team including Kosuke Matsuda to add useful functions and simplify tasks like DOM manipulation. It is based on prototype-based programming and aims to make JavaScript development easier by abstracting away browser inconsistencies and providing useful utilities like Ajax functionality and DOM manipulation methods inspired by jQuery. The presentation introduces Prototype.js and its capabilities for simplifying JavaScript development and enhancing web applications.