QGIS question

By operning a multipolygon shape file, and enabling Vertex Tool (under Edit->Edit geometry) am able to see the X, Y coordinates of the points making the polygon. When i use Vector->Geometry Tools->Extract Vertices (on a temporarly layer), the vertices are defined as distance/angle - it's unclear what is considered to be the root node of these distance/angle data.
Anyone with an idea on how i can locate this root reference in by data?