Raphael.js is a JavaScript library for creating vector-based graphics. It allows developers to work with SVG and VML across browsers similarly to how jQuery works with the DOM. Raphael.js provides an API for drawing shapes and setting attributes on a graphical canvas. It supports events, animation, and other features while having a small file size. Raphael.js works across browsers while native SVG, VML, and Canvas have varying browser support. It allows creating scalable and accessible graphics for the web more easily compared to using images.