This value reflects the cards ability to process geometry using vertex shaders (or fixed function operations in older cards).
How To Calculate It
Vertex Operations/sec = (# of Vertex Pipelines) x (Core Clock)
Does It Matter?
Not really. I honestly can't think of a single game in which vertex processing capability is a limiting factor.
Long VersionVertex operations transform raw 3D geometry into the 2D plane of your monitor. Vertex pipelines also eliminate unneeded geometry by detecting parts of the scene that are hidden by other parts and simply discarding those parts.