SVG is a platform for two-dimensional graphics. It has two parts: an XML-based file format and a programming API for graphical applications. Key features include shapes, text and embedded raster graphics, with many different painting styles. It supports scripting through languages such as ECMAScript and has comprehensive support for animation. Source: W3C (http://www.w3.org/Graphics/SVG/About.html)
Although SVG is an excellent format for delivering graphics in web documents, it has not been widely adopted in large part because the most widely used web browser in the world - Internet Explorer - does not have native support for SVG.
You can help promote the adoption of SVG on the web by encouraging web users to browse with software that includes at least partial native SVG support. The most recent stable releases of Opera, Safari, and Firefox include at least partial native SVG support.
Also, there are free SVG viewer plugins available for users that browse with Internet Explorer: Renesis Player and Adobe SVG Viewer.