Jack is right (he was a Sikorsky Test Pilot, after all!) The HV curve shows the area where the loss of the FIRST engine (one engine left, working its heart out) will result in a hard landing or worse, under the specified "worst case" environment. This means max gross weight, still air, so that lighter weights and some wind above perhaps 5 knots will result in much better aircraft response.
Even though this is in the limits section, it is generally treated as a performance chart (chapter 4) by the FAA, since strict adherence to the chart could preclude operations to rigs, heliports and such. For example, on short final to a rig at 125 feet and 10 knots of speed, you are clearly in the avoid area. Every day.