SVG is a vector graphics format: you write a description of objects in the drawing as a set of declarations: "red square at (50,50)", "the word vector rotated 30° and flipped". Then the browser renders the scene graph. The underlying XML isn't too verbose and the syntax for transformations and paths and the like is a shorter text format. SVG is remarkably capable in what it can draw and browsers do a beautiful job of rendering with anti-aliasing. Given how rare SVG usage has been it's amazing how good the implementations are.
This blog post contains some simple SVG: if you don't see a wind rose in the upper right click through to my blog. Should work in IE9, Firefox 4, and Chrome. (Doesn't work in Safari and older Firefox because of XML namespace issues unique to my blog). If you view the source you can see the code for the diagram. It's basically a bag of <path> elements, each of which draws a wedge and translates it.