UPDATE: I have since re-written the code for this in my plugin – to view the latest method – look here: http://sterlinghamilton.com/scalable-vector-graphics-plugin/
What the deuce is SVG?
Scalable Vector Graphics (SVG) is a family of specifications of an XML-based file format for describing two-dimensional vector graphics, both static and dynamic (i.e. interactive or animated).
The SVG specification is an open standard that has been under development by the World Wide Web Consortium (W3C) since 1999.
Basically, it means you can have an image that looks really crisp and clear, and it can become really small or really large without losing quality.