What is SVG?
SVG (Scalable Vector Graphics) is an XML-based vector image format that describes shapes with mathematical paths instead of a pixel grid. This means SVGs scale to any size with no quality loss and are usually tiny for simple graphics (icons, logos), but they are a poor fit for photographs, which have no clean vector representation.
Example
<circle cx="50" cy="50" r="40" /> draws a circle that looks sharp at any zoom level.
Related tool
Try it on ToolSphere — runs entirely in your browser, nothing is uploaded to a server.