Concentricity Dimension: This tells if a line reducible feature is on the same line as another line reducible feature. This is intended to see if a pin and a hole will mate without interference. If the pin is not concentric to a hole (i.e., the pin is angled too drastically) then the pin will interfere with the edges of the hole. Make sure when measuring a cylinder that you measure 3 points at the top of the cylinder, 3 points at the bottom, and the rest of the points in between the aforementioned points.
For more information on Concentricity please review the attached download below and this linked document here.
Click here to download: Measure GD&T Functional Explanation