DiagramPlot[{{x1, y1}, {x2, y2}, ...}] plots the Voronoi diagram of the points {{x1, y1}, ...}.
DiagramPlot[{{x1, y1}, {x2, y2}, ...}, {q1, q2, ...}, val] plots the points {{x1, y1}, ...} as well as the diagram described by the vertices q1, q2, ... and the vertex adjacency list val.
Valid settings for LabelPoints are True and False. With the setting LabelPoints->True, each point is labeled according to its position in the input list.
Valid settings for TrimPoints is any non-negative integer. Regardless of the setting for TrimPoints, the PlotRange is always large enough to include all the points {x1, y1}, {x2, y2}, ....